→ [root tip] [HowTo] Check if your AUR build scripts have been updated
The problem with having AUR enabled on stable branch is well documented - just search the forum.
I have a taken a lot of heat over the years because I have pointed out the problems with indiscriminate AUR usage on stable branch.
But as pointed out above - the disable in the GUI does not prevent usage of AUR - but you will be more aware of what you are doing as it is no longer point, click and forget.