That sounds very neat!
Did you happen to see my question here? PEP 639, Round 2: Improving license clarity with better package metadata - #14 by ofek
I really think that’s the only critique being expressed by anyone i.e. that the cost/benefit analysis described in https://www.python.org/dev/peps/pep-0639/#source-metadata-license-key does not justify the rejection of the idea.