Well, that section is talking about CPU-bound tasks, and both threads and processes are valid choices for CPU-bound tasks, with different tradeoffs.

I think there is often a lot of confusion around that because a lot of tutorials simply say to use threads for IO-bound tasks and processes for CPU-bound tasks, without going deeper into the differences. Threads can easily share memory which often increases complexity and requires locks to run safely, with processes you avoid locking (including the infamous Python GIL) but also have to pass around data which might hurt performance.

Regardless, it still doesn't make sense to say threads are only appropriate for IO-bound tasks, the official documentation [0] seems to lean towards preferring threads for mixing IO and CPU-bound tasks, and processes for purely CPU-bound tasks.

[0]: https://docs.python.org/3/library/concurrent.futures.html#th...