I think this has nothing to do with anything.

I am the king of scruffiness. AND I never dress up for F. On the contrary, I dress down and usually fly wearing flip flops and shorts.
I don't think there has been a single instance in which I have been asked "Are you in F/priority?" Never have I ever perceived either that I've been treated differently for not dressing up or looking the way I look.

I think people here underestimate the experience of the GAs, at least the AA personnel, because the GAs know better that there is not an "F" look, since the F population is pretty diverse and they've seen it.

There are 100s of reasons of why the GA might have asked the question "Are you Priority?". That the question is asked doesn't mean that the GA is judging. I wouldn't have been bothered at all. Just say "Yup" and move on.