Promised myself I wouldn't. Oh well. This one time.
OK, interesting question for June, but lot of slicing and dicing called for: Think your first premise is wrong on its face, your second needs proof before being accepted, your terms are really fuzzy, and your conclusions do not follow. Other than that, all good.
1) Wrong on its face I: Most foam cores these days are milled, nor injected. And are barely recognizable as the stuff we think of as foam. Dynastar and Stockli come to mind. Some beginner skis may still be injected with something that looks like a Rossi B2.
2) Wrong on its face II: Far as I know, modern milled foam still needs to be bonded to laminates. So glue's still involved. Again, no one I know has injected foam into a cap since Salomon and Rossi gave it up years ago.
3) Needs proof: Not clear in any case that foam on the levels that matter for resisting forces on the ski is significantly less variable than wood. Suspect the (assumed) higher variation in wood cores washes out statistically by the time you compute flex. Which is an average for a cross section of the ski body, not a scanning electron microscope cross section of a micrometer of the core.
4) Needs proof: Not clear that glue is necessarily a major source of variation in flex. Thick, less-uniform layers of glue are typical of startup indies - ON3P's great thread over at TGR talks about that - but experienced modern factories tend to use as little glue as possible and I suspect that many use robots for application. But even where skis are still "handmade," like Stockli and Kastle, do not think little old men are applying glue with a paint brush. Finally, I've been told by makers that glue impacts weight, not flex. This makes sense, since the other materials - core and the glass or carbon or metal - seem to be the major determinants of flex.
5) Needs proof: Taking an individual ski out of the production line and working on it make it "right" might work for a garage indie with a staff of 3 and production run of 300. But think how much skilled hourly labor in Austria that would cost, versus just tossing the ski. Doesn't seem to fit with basic economics. At most, a skilled worker near the end of the process might make some small trim or tweak that takes a few seconds. Ever looked at the tips of a ski edge on? No two quite fit together the same way, even to the naked eye. Does it matter in terms of ski performance? Nope. Does it affect sales? Nope.
6) Needs a linking argument: Not clear that Bode breaking skis and sweating over new ones means all skis have high variation in flex. Might mean that elite racers are highly attuned to small amounts of variation that the rest of us would not notice, since it's washed out by other larger sources of error like how we ski. There's no point economically to providing more QC than is needed to achieve a certain level of customer satisfaction.
More likely, given his history - Bode's a head case about gear - that like elite performers in other arenas, his seeking out of perfect matches for new skis is actually a behavioral tic that calms him down and gives him confidence. Analogy: Blind tests show that the best flute players in the world cannot identify what metal the flute is made of, if the weight is adjusted. Or that violinists cannot identify a Strad. But those same players swear that a gold and silver flute sound distinctly different, and that a Strad is unique. Our brains want to think we have more sensory and kinesthetic acuity than we do.
7) Fuzzy terms: Ever looked at a scan of a good knife blade? Or a diamond? Totally non-uniform. Lot of variation in the inclusions and geometry of same. Random, too, which can be more important than whether there's variation. But at the level of physics that matters when we cut with the blade or flash the diamond, very uniform, non-random mechanical properties. So little variation. It's all relative. How do you define "variation," then? And what's a lot or a little?
8) Needs proof: How do you know that skis with different flex numbers were "meant to be the same?" Or that Bode should have been able to find "identical" skis? As you know, there is no "same" or "identical" in any manufacturing. Rather, there are confidence intervals. Seems most likely that the company does a run of skis with a particular confidence interval for flex, then tests them post-production. Given the statistics of manufacturing, some of that run will show up outside the confidence interval. They will either be discarded, which is how a lot of QC works, or assigned a different number if their measured flex falls within another confidence interval. It's possible the confidence intervals are narrower - higher QC - for elite racing skis.
OTOH, it's just as possible it's wider as you go up the racing ladder. Why? Because far as I know, WC racers do not ski on gear made by the big automated presses and robots. Separate facilities. In Bode's case, he was forever asking his sponsor to change around the flex pattern, or make everything stiffer. So his skis were more literally hand built, and thus had to have more variation. Which prolly fed his athlete's obsession over gear. I know this is true for pro tennis, where each sponsored pro has his or her own mold, and is constantly asking for tweaks. (Of course, matches are not won or lost on a racquet being minutely different than the last, but on the players making mental mistakes or changing their mechanics or not adjusting to the opponent. Ditto for skiing, substitute course for opponent.)
8) Conclusions do not follow: The "art, not science" aphorism has never made any sense to me. All science has luck and creativity and human fallibility in it. And all art has scientific foundations. As technology progresses, the amount of individual fallibility, and variance, is reduced. But not eliminated. In any case, the amount of error in a product's performance is generally set by the price point, not by what's technologically possible. We don't expect cars to last as long, or be as error free, as planes. And we love "handmade" stuff that's highly variable if it's really hand made.
Meanwhile, "black boxes" have to do with thermodynamics. If a ski maker had so little ability to "see" inside its manufacturing processes that they're opaque, that company will be toast. Right away.
9) IMO the relevant question is just the opposite. Why do we expect so little variation in industrial products? We worry about flex or tiny topsheet blems in skis that we'll ding up in one run, we shake our heads over jeans of the same length that actually differ by 1/2 inch, or toss back a pair with a dropped stitch. My hunch is that we like to think that the reason we can't ski worth s*t is our gear. So if we get uniform, perfect, gear, lovingly crafted by little elf-robots in the Black Forest, for the pure love of making skis, we will turn out uniform, perfect turns. And those perfect jeans will make that person at the bar look at us in a whole new way. Right...