Unfortunately, the current likely answer re updating vanilla distutils to handle the new standards is "we won't". The backwards compatibility issues involved are just too hairy for us to start enabling by default in the standard library, and I've become convinced that coupling the build and installation tools to the language version is fundamentally a mistake anyway (hence the bundling approach in PEP 453).

Instead, we're hacking around the metadata side of the problem through the fact that pip always runs setup.py under setuptools (even if the setup.py only used vanilla distutils) and encouraging the use of cross-version compatible tools in other cases (with setuptools being the current de facto choice, since the distlib APIs are still considered experimental).

For this particularly case, I don't see any harm in bringing distutils in Py3 back in line with Py2, especially if it's also consistent with setuptools.