I only see the article mentioning CPU (and GIL) once, but in any case, the generalisation is correct for any pure Python code. You can only release the GIL in extension code (for CPython), and in that point you’re not really dealing with Python threads (although you may use Python’s wrapper API for threading), but its underlying implementation (e.g. pthreads) instead. The framing of the statement is very important, and I wouldn’t call it overgeneralising in the context of this particular article.