Posix sleep takes seconds, but Windows sleep takes milliseconds.

Compare to solution used by std::this_thread::sleep_for, which uses explicit typing to ensure the caller knows what's what.

Example of possible better interface:

QThread::sleep(qSeconds(1));

...where qSeconds returns a typed object. Alternatively also providing qMiliseconds and qNanoseconds would make the interface of QThread cleaner IMO.

I understand that this would probably be something for Qt 6, and there should still be a compatibility flag that allows existing implementations to remain compatible.