Note that $Config{archname} equality isn't enough

UPDATE: I think I've now figured it out - that you were alluding to the possibility of different toolchain involvement, different external dependencies, etc.

I didn't know that.
This would also imply that 2 perls with the same version number and same $Config{archname} could be binary-incompatible.
For over a quarter of a century, PPM installations have relied entirely (and flawlessly) solely upon version number and $Config{archname} to determine which package to install - and now you're telling me that's insufficient.

Can you please provide an example of a difference that could cause incompatibility, yet not alter $Config{archname} ?

Cheers,
Rob