On macOS Big Sur (11.y.z), the return value of distutils.util.get_platform() records in some cases the minor version of OS. For example:

- with a Python 3.9 built on macOS 10.0.1, distutils.util.get_platform() will return macosx-11.0-x86_64
- with a Python 3.9 built on macOS 10.1.0, distutils.util.get_platform() will return macosx-11.1-x86_64
- if MACOSX_DEPLOYMENT_TARGET=11.1 was set at build time, then distutils.util.get_platform() will return macosx-11.1-x86_64
- if MACOSX_DEPLOYMENT_TARGET=11 was set at build time, then distutils.util.get_platform() will return macosx-11-x86_64

This has important consequences for wheel and pip, which use the return value to determine platform tags: https://github.com/pypa/wheel/issues/385

From the API Reference (https://docs.python.org/3/distutils/apiref.html), it is not clear what the expect return value is. Given that previously, the return value of distutils.util.get_platform() was dependent only on the macOS major version, I would expect this to be the case. Therefore, distutils.util.get_platform() should return macosx-11-x86_64 on all Big Sur (macOS 11.x.y) versions.

PS: This is not directly related to another issue with MACOSX_DEPLOYMENT_TARGET
https://bugs.python.org/issue42504