What if it wasn’t part of stdlib itself, but it was a package shipped with Python, like pip is nowadays? If someone’s life would be materially improved by license metadata, or any other new standard, they could upgrade their copy of simplebuildbackend [1]. Everyone else can stay on the default version and it would probably still work (ignoring the new metadata). Users of Python 3.11 (and possibly even older) can install it using pip.
The bigger problem is, of course, designating the one true simple build backend, or developing it from scratch. ↩︎