Not completely unconcerned, PSF did donate $10k to PyPy last month, so they do recognize some importance for speed, even if it isn't CPython's priority.
(and PyPy does break some python APIs and expectations, speed does come at a small cost, after all)
I was specifically thinking of `gc` at the time of writing, which is a part of python, not CPython. (though it only has reason to exist as a part of CPython)
but yeah, for... probably 90%+ of use-cases, it is the PyPy<=>CPython differences that are more notable
(and PyPy does break some python APIs and expectations, speed does come at a small cost, after all)