There is a specific Python function in 3.9 for it:

https://docs.python.org/3.9/library/gc.html#gc.is_finalized

So it may sense to add a function to query if an object is finalized, but I am not sure it makes sense to allow to mark an object as finalized because that could mess with the GC algorithm.

Certainly exposing the macros per se may be a bad idea because there are too many implementation details there (like where the flags are stored) so at least a new function will be needed.