Seems like a stretch. We are shown multiple times that the Avatar as a concept and the person are different entities. Aang in the show only showed interest in girls and Korra was bisexual.

as far as we know in his entire life he had exactly one romantic interest and any flirting he did was with also femme characters. of team avatar if anyone's pan it's Toph strictly because she's not gonna let some made up gender binary tell her who to be attracted to, she won't let anyone tell her what to do

I think it's because the avatar has been all sexualities at different times.