The gist of what GP meant is that Python does not exactly follow SemVer in their numbering scheme, and they treat the middle number more like what would warrant a major (left-most) number increase in SemVer. For example, things will get deprecated and dropped from the standard library, which is a backwards-incompatible change. Middle number changes is also when new features are released, and they get their own "what's new" pages. So on the whole, these middle-number changes feel like "major" releases.
That being said, the Python docs themselves [0] call the left-most number the "major" one, so GP is not technically correct, while I'd say they're right for practical, but easier to misunderstand, purposes.
> A is the major version number – it is only incremented for really major changes in the language.
> B is the minor version number – it is incremented for less earth-shattering changes.
> C is the micro version number – it is incremented for each bugfix release.
The docs do not seem to mention you, though. :P
[0]: https://docs.python.org/3/faq/general.html#how-does-the-pyth...
That's ultimately the point I was trying to make; my inner pedant can't help but feel the need to push back on people using versioning terminology inconsistently, but in practice I don't think it really made much of a difference in this case.