It would have been shocking to me because he played quite a bit every single game last year (unless I'm mistaken). We lost one of our better interior lineman, it's a somewhat thin group, he would have been a senior (with two previous years starting experience), and even with this list, he'd be in the two deeps. I would have been pretty surprised if Dovich would have jumped Mayes.
Let's say all of these scenarios play out:
T: Wright
G: Calhoun
C: Weyler
G: Olson
T: Greene
Our only non-freshman backups would have been Mayes, Dovich, Oseland, Connolly, Schlueter. So, even when giving your analysis the greatest benefit of the doubt (Olson and Dovich are both better right now than Mayes), he'd still firmly be in the 2 deeps and the 7th best OL on the team.
So yeah, it'd be pretty surprising to me if the 7th best OL on our team didn't get significant PT (that would be an incredibly healthy OL) and it would be pretty surprising to me if a bunch of true freshman and/or guys he has always been higher than on the depth chart passed him.
This transfer isn't the end of the world or anything, but it would have been pretty shocking to me if Mayes was on our roster and didn't get much PT next season. He was also kind of a perfect OL. He is a senior, so he would give us depth this year and not take up a roster spot for PJ to recruit his guys. So, I doubt PJ pushed this transfer at all (I'm not saying you did, but some people seem to be implying it).