Having now seen a bombproof you can't bend it shift on a scope that provides a bomb proof you can't bend it range, i'm going to see how my other scopes behave as well... as their in the cupboard it should be easy to do them in a session if the weather plays ball.
It does make me wonder about the little shifts i used to see on the guns, and perhaps i was persuading myself to cheat the ranges previously... the march is about the only scope i've spent time with that wont allow you to lie at 55... if it's out it's blurred... you might wander a yard or perhaps a tad more but i reckon 2 yds out and it's obvious, where as the walther/tasco/debens i've had before have demanded a detail to confirm a range, else they could have been deemed in range.
Like you, i suspect AO scopes are less prone to it... perhaps that's because your directly shifting the lens, rather than using a mechanism.
I also wonder if 'lesser' scopes are shifting, but are more vague to start with, ie they shift in a band that's not noticable unless it's a really big shift. I know I keep harping on about her, but the march is needle sharp repeatable, so if it moves, you notice it... it hasn't really got any vagueness to it... i reckon it ranges at 70yds about as well as many do at 50.