Austin, the character, also has the advantage of being written as fully committing to the free love swinger movement of the 60s. It would not stretch credulity if his 90s era handlers were paranoid about Austin finding out his partner is a gay man, but Austin himself is completely nonplussed by the news. Hell, he could even allude to having same-sex experiences of his own (“You know, when you are at the bottom of an orgy pile, you don’t always know where your bits and bobs are going, and you certainly don’t care. Yeah, baby!”)
I dispute the premise that SBMM is a fundamental requirement for PVP to work, though obviously it’s become intertwibed with the genre that a game choosing not to use it is going to have a more difficult go of it to onboard folks.
There was a time before SBMM after all. A time of server browsers, admins with chips on their shoulders, GameSpy, and “unofficial” map rotations and rules.
Now, for about a billion different reasons, this model is not going to make a comeback and become king again. But, I just wanted to mention that MM is not as “fundamental” as your comment indicated.