As an example, CVE-2022-30190 was patched in June 2022.
However, running patch_review.py 2022-jun will report no mention of it. Why?
Well, MSRC lists "it" as being released in May rather than June. "It" being something said about the vulnerability, not the updates themselves.
I suspect that users of patch_review.py may expect the tool to list what updates are released in the specified month. Not what bulletins.