No, I'm still skeptical. I can as easily believe that the lead tooth and engaged roller take the vast majority of pressure and thus wear at a nearly zero link angle.
I think the wear is spread over several teeth, although I have no way of measuring that. I couldn't find anything on that through Google. I think the reason we replace derailler chains at 0.5% stretch rather than 3% is that as pitch increases, more load is taken by a single tooth, causing excessive wear. If you change chains frequently, they run fine on old cassetttes because new chains don't cause much wear.
For the value, if the difference is significant then why doesn't flipping a worn chain on an imprinted cassette cause lousy shifting? Or does it? And if it does, what's the point?
Flipping the chain doesn't cause poor shifting for the same reason a new chain doesn't. You need to change out chains at very low levels of wear. The point is, if I can rotate any part to find a region of less wear, why wouldn't I do that? It's really no different than when we switch the running rigging on our sailboats end for end. You get more life because the wear points have changed, and you get it for free.
em