What complicates the issue for AIX (and reminds me very strongly of the MacOS and manylinux situations, both of which were defined after the original tag PEP, and so contain additional insights) is the business of certain tags being compatible across multiple AIX versions.

That's something that needs to be fairly clearly specified, so that implementors and maintainers understand the design. And even more so for a niche platform like AIX, as we can't rely on a platform expert being available. (Consider for example a pip issue "this wheel says it's compatible with AIX x.y.z, my machine is AIX x.y.w which is documented as compatible, why isn't it working?")

It's possible that all of this may not have any relevance to the specific change to core Python, but it's hard to be sure of that when there's nothing other than your explanation to go on. A tagging spec would act as a clear reference to work from (even if it's basically just you writing up your knowledge, doing so would at least allow people to say "hey - I don't follow that bit, can you clarify").

To put it another way, you need somebody to sign off on this change as correct. You'll have an easier time of getting that if there's a written up spec that Python developers can refer to, without having to go back to (and understand) all of the AIX source material that it's based on.