After a few days of unexpected plumbing/sheetrock/painting issues I'm just now finding some time to catch up a bit.
I'm certainly on board with the Virtual Bump idea and all its geometric and mechanical implications in the real world! True, it's a perceptual thing but then again, most of what we experience when skiing is a perceptual thing. Maybe I'll write something up on this as I get more time.
Re-reading that material I'd say my perspective on rebound hasn't changed at all since then. Stiff skies might provide a tiny bit of actual 'spring' but nowhere near enough to make much "momentum difference" to the overall skier.
I think perceptions are skewed by skiers who compress their skis into a big bend with the full weight of their whole body, then relax their legs letting the compressed skis 'spring back' ejecting their feet back up toward their upper body. Sure, the skis have enough tension to toss our feet back at our upper body, but not enough to toss our whole body around.