Well, you're suggesting a thought experiment in reliability testing. Obviously, expectations and previous experience figure into any evaluation. Not just "subjective" measurements, either. Even using a micrometer. All part of intra and inter observer error. But does that = "tricking?" Does the fact that we have biases mean that any measurement that includes those biases is useless?
Umm no. Let's disregard the last 20 years of neurobiology that indicates "hunches" and systematic biases often represent connections between the prefrontal cortex and the limbic system, such that we are drawing on success or failure of previous algorithms to hone our efficiency in solving the problem on the table. Let's also disregard entire new schools of statistics that find discriminatory power increases when prior outcomes and expectations are included. After that, we still know that brands do have characteristic shared design parameters and production specs that produce a brand "feel." That's deliberate, as you know, and is driven by corporate marketing decisions. When a brand changes it's design goals in a big way - Salomon comes to mind when Atomic acquired it - the alteration of brand feel and performance is often a big deal. Everyone notes it.
So I'd argue back that figuring previous knowledge into a current hand flex, isn't subconscious magic, it's just one way we humans make current evaluations more efficient, and predictions more accurate. My hunch that 2015's Rossi E88's will retain a damp feel, have a fairly light weight, with fairly soft tips and modest rocker that don't overpower the skis's carving ability, is worth betting on. And it isn't "cheating," since it's simply incorporating previous data that has proven correct. Companies generally strive for product predictability as long as it's associated with profit. Which is why a Big Mac is designed to taste the same anywhere.
The counter argument goes something like this, if you wanted to make another thought experiment: Correlate various ski attributes against each other. Cluster the results. The resultant group membership will have no significant overlap with those groups simply formed by brand. Interesting conjecture, but I'd doubt you'd find anyone else on these threads that'd buy it.
Fact is, while there will be some overlap, given the sheer number of products out there competing within each width range and skier demographic, Blizzards will be more like other Blizzards than like Rossignols. Where it gets interesting is if you compared brands that had common engineers or designers or production facilities. No accident that Blizzards and Volkls and Nordicas share some qualities. Say they comprise a larger cluster different from the Rossignol and Dynastar one, which used to include Salomon too. So I really don't see how this means that it's trickery to flex a Volkl, or ping it, or whatever, and glean a family resemblance to other Volkls. The flex will be one of the intra-group correlations.
As far as flexing by hand, meh. Some people don't know how or where to flex a ski anyway, so it's like kicking a tire. Others do. Someone here, Sierra Jim, maybe, say back when that he could flex a ski and tell most of what he need to know about it. I believe it. Same argument as mine here, unstated. But consider that Fri Flyt has been published well-respected flex charts for years now, using weights hung at various points along the ski and measuring deflection. Used paint cans originally, I recall. And that's the same deflection you or I try to produce in a store. Only instead of measuring cm of deflection, we estimate differences in resistance to muscle force between the ski we're pushing at and the one next to it. Or last week. Obviously more sources of error. But some people are pretty good at estimating force. Moreover, if you can hand flex the front 1/3 of a Mantra and then do the same for a Prophet, and not be able to consistently note that the Mantra required more force, get thee to a neurologist. If you can then ski the two, and not note that the Mantra has different handling characteristics than the Prophet that are partially attributable to the differences in front flex, get thee to a ski school...