USES=python should complain if there are unknown components in USE_PYTHON. At the moment everything is just silently accepted. For example USE_PYTHON= autoplist distutlls is accepted, but it should be an error (distutlls should be distutils here) since it doesn't really do anything There is only a finite list of acceptable keywords for USE_PYTHON, so it should be possible to check this and refuse the build if there are unknown keywords in it.
Sounds like something that's very worth doing across the framework in a single bug (or multiple issues under a meta bug), for all USE_*'s / Uses/* component arguments.
Patch to do this here: https://reviews.freebsd.org/D19569
A commit references this bug: Author: tobik Date: Thu Apr 18 13:16:45 UTC 2019 New revision: 499257 URL: https://svnweb.freebsd.org/changeset/ports/499257 Log: Mk/Uses/python.mk: Flag unknown USES=python args and unknown USE_PYTHON features PR: 235901 Approved by: mat Differential Revision: https://reviews.freebsd.org/D19569 Changes: head/Mk/Uses/python.mk