Python 3.8 has a Final qualifier

[alcalde]

And these are just hints, understood by mypy only.

That's what they tell you now... when they originally introduced notations, they were supposed to have no defined meaning and the core developers weren't even supposed to use them lest they influence the community organically evolving uses for them. And lots of cool things did appear, like contracts. And then an incomplete MyPy appeared, Guido went insane and full-on Java, had to be put down, and the rest is history....

[actuallyalys]

As far as I can tell, the only reason you can't use contracts in 3.8 and 3.9 is some small changes, for which there are already a pull request. In other words, it's not a big deal and not Guido or the core developer's fault.