I'd be inclined to think it's because trans people are more likely to engage with anti-trans posts.

I'm a cis lesbian and I only get pro-trans content, BUT I do get a lot of 'random bisexuals shitting on lesbians' content.

I've also noticed that when I scroll away from political posts from the left, it almost immediately tries to give me political posts from the right. The algorithm doesn't seem to pick up that my main concern with political content is whether or not it's FUNNY. The only political content I want to see on TikTok is shitposts, but the algo seems to operate under a pretty basic 'If scroll past left/right, then show right/left'.