There can always been regressions with older cards regardless of the manufacturer. Focus is mostly on those which are available to buy at the market. Linux as an OS is mostly used to get older hardware up to speed with newer software.
AMD has actually a good track record and I’m in direct contact with one of their kernel developers. When stuff can be recreated on the last stable kernel, as in 6.12 it can be an issue. When you test things on RC, you can spot things which may come up and possible can be fixed before the final release of that kernel series. However, we should not mix it.
Next release of Mesa is scheduled for the 18th of December: Release Calendar — The Mesa 3D Graphics Library latest documentation. A list of upcoming commits can be reviewed here: https://gitlab.freedesktop.org/mesa/mesa/-/commits/main?ref_type=HEADS. A list of issues here: Issues · Mesa / mesa · GitLab
As a distro you have to see what the best overall way is. Sure, there are some regressions or issues with other cards like from Nvidia or Intel. So if you know it is the drivers and you know on how to hold back or recompile the packages, it is fine. We just have to decide if we want to ship it to the stable branch or not yet.
Based on the current MR the patches added by Arch are older versions and in some edge-cases 24.3 series still crashes: egl: implicit modifiers fixes (!32535) · Merge requests · Mesa / mesa · GitLab