I think we're starting to see more of this sort of thing happening now with Proton and Wine gaining prominence in the Linux community. Some games (Elden Ring comes to mind) have bad enough PC ports when they come out that the compatibility layer can incorporate a hotfix to improve performance, while users of the software on the original platform still had to suffer.
GPU driver packages are already a huge collection of workarounds for bad game engine coding. An Nvidia employee once told me that one of the easiest ways to squeeze out a few extra frames on your old machine is to rename the game executable to hl2.exe.
What it should do is ensure some things not relevant to Half-Life 2 were not done, thus getting better performance for this game in particular, but there is no guarantee that same optimizations work for other applications or games, so one should not expect an overall improvement.
Unless they are doing some silly things like dropping quality, but that's the "everything else the same" point.
If not, why not have this enabled as default behavior instead?