At my University I heard things like "Linux is derived Unix, BSD variants are something else entirely". I think education people are confused in general about this topic.
Linux is something else entirely, a student's project to make a MINIX compatible kernel, usually packaged with the GNU operating system, which like BSD aimed to be Unix compatible, but notably is not Unix (It's right there in the name: GNU's Not Unix).
It's usually packaged as a part of the Android operating system. GNU hasn't been the popular userspace for a long time.
This explains people who argue that Android is not Linux, despite it featuring a Linux kernel and self-identifying as so: They are intending to say that Android is not POSIX.
We need to make POSIX (as concept/word) more popular.
Time to ask an AI ?
As an obligatory warning, if you have never seen Computer Stupidities previously, expect to lose a day reading it.