Just did some testing with the dozen or so titles (mostly Koei Tecmo musous) I have that require very specific GE Proton versions due to the video codec regressions that occurred awhile back and that GE10-12 finally addresses. The results were a mixed bag, but this is definitely a positive and long-overdue step. A few games were able to shed their late 8.x/early 9.x requirements finally, but others (particularly those released 2015 or earlier) still have the same problems and have to rely on pretty old GE versions.
Samurai Warriors 5 and Warriors Orochi 3 still need GE9-2, Samurai Warriors 4-II and One Piece Pirate Warriors 3 still need GE8-25, and both Dynasty Warriors 8 and DW8 Empires still need GE7-55.
Buuuut Samurai Warriors 4 DX, Samurai Warriors Spirit of Sanada, Warriors Orochi 4, Warriors All-Stars, and One Piece Pirate Warriors 4 all got successfully bumped up. And in non-musou land Pinball FX and Postal Brain Damaged did too.
Some would say compatibilty but they go hand-in-hand so I’d say both. It’s very game/issue-specific though. Some games/systems will have huge bumps from 7.x to 10.x but others none at all… just depends on why they didn’t have great performance to begin with.
These days Proton is in a good spot so it’s a lot of weird outliers (like the codec thing) that weren’t necessarily showstoppers, or support brand new games need which is why they may seem more significantly impacted.