Silly to use the term UNIX at all, it was replaced by POSIX which is still not perfect but less amorphous. Anything that is POSIX-complaint or near-compliant is a usable system for someone who would have accepted a UNIX system last millennium.
I actually liked SUA more than WSL, which I like more than WSL2, since it seems like they keep moving farther and farther away from making Windows actually POSIX compliant and instead just offering a container for your pesky POSIX needs.
In other words, for 29 years now, "this is UNIX" means "it passes the POSIX test suite". The terms are basically interchangeable.