The blog post is actually a bit imprecise; when it says "almost every Python program that touches cryptography goes through pyca/cryptography", that's only true if you don't count TLS. TLS in Python is usually done through the standard library's ssl module, which is mostly just a wrapper around OpenSSL. So that's basically an entirely separate workstream that doesn't really have anything to do with this post.

Brand new PQ in pyca is cool too.

When you make an https request in Python, which library does it use for the TLS TCP socket wrapper?

OpenSSL.

The TLS PEP was never accepted or implemented.

There's a rustls PQ issue.

Only certain things in Python use pyca/cryptography.