Minor issues prevent compatibility regen'd interpreter loop

[DinoV]

Bug report

Bug description:

There's some minor issues that prevent a re-gen'd interpreter loop for a PEP 523 replacer from working as ideally as it would. One example is that the specializer won't kick in even if the re-gen'd interpreter is compatible.

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Linked PRs

• gh-143531: Use macro to check if PEP 523 is hooked #143532