First off, that "feature" was never really a thing guaranteed to be supported, there where always CPU combination that caused trouble, more so from different vendors but also intra-vendor especially on different generation, there are some CPU side effects that just cannot be abstracted away in migration (often working most of the time, but with bad luck breaking occasionally).This feature (possibility to migrate without any problems from different CPU generation) was very very unique cool feature, it will be a pity to lose this feature....
That's why we recommend using homogenous enterprise hardware for all production setups.
Secondly, it still works for lots of different model combinations, so it's not like getting impossible to do.
Also, we naturally backport a fix, if any, but just going from some promising commit messages will give you a big set of patches to cherry-pick, possibly bringing a lot of regression with them as a) sometimes that just happens and b) they were developed for a different kernel base. That's why I asked if you already had good experience with the patch that you linked, as I noticed that one too a few weeks ago but stopped bothering once I saw the fpu module changes that may break existing (recommended homogenous) setups, so putting in effort there must be waranted. Maybe I'll give it another try upcoming weeks.