> Pre-alpha are much better as .dev releases.

No, they are correctly using semantic versioning to indicate pre-alpha releases. https://github.com/astral-sh/ty/releases https://semver.org/

Python doesn’t use plain semver: https://peps.python.org/pep-0440/

The reference Python implementation, written in C, doesn't use semver. But other projects in the Python ecosystem are generally assumed to unless stated otherwise. For example, Setuptools does (but not pip: https://pip.pypa.io/en/stable/development/release-process/).

It is the sixth alpha release. They haven't yet released a stable version – this is their sixth alpha release before that.

What am I missing here?

I was replying to a post that said "Please be aware this is pre-alpha software." presumably trying to make a distinction from "alpha software".