The law in question only prohibits biological males from participating in female sports. It does not prohibit females from joining boys teams.

There's a simple reason for that - the second sentence is required under current interpretations of Title IX, while the first is not. The argument for that is about girl's sports being a sort of protected space for girls, so it's OK to bar non-girls (however your jurisdiction chooses to define that) from girls sports, but "boys" sports are actually for everyone who can compete.