It makes sense in terms of trusting the package index, but it's inverted from the original design goal: the point of end-user signatures on package indices is to eliminate unnecessary package index trust, not reinforce it.
If you already trust the package index, then mandating HTTPS and strong cryptographic digests is going to be far more effective (and secure) than some kind of PGP key attestation scheme.
Without an easy way to verify the keys, the signatures are useless. Which is why PiPy is removing the GPG keys all together.
I know that; the GP is describing a countersigning scheme, where the package index (qua trusted entity) countersigns for the signing key, which the dev then uses to sign for their package.
> Without an easy way to verify the keys, the signatures are useless. Which is why PiPy is removing the GPG keys all together.
Agreed entirely; I'm the one who wrote the analysis in the linked announcement :-)