> Another change that might be needed: ensure that sysconfig.get_platform() 
> does not return "universal2" as the binary architecture when the compiler 
> does not support arm64.

Hmmm... _osx_support.get_platform_osx() contains the following comment:

        # Use the original CFLAGS value, if available, so that we
        # return the same machine type for the platform string.
        # Otherwise, distutils may consider this a cross-compiling
        # case and disallow installs.

That indicates that fixing the value of sysconfig.get_platform() when using a "universal2" python on a system that doesn't support arm64 might break distils. 

I haven't done further research on this. In general I'd prefer to create the correct platform tag, but not if that results in not being able to install extensions.