Using "TRA" to describe trans people isn't neutral, it's deliberately invoked to mimic MRA, or Men's Rights Activist, and when used to describe trans women is a form of dogwhistle misgendering.

It's a hostile and antagonistic term of abuse, much like when trans women are referred to as "TIMs", it's the subtle, dogwhistle misgendering that's the point.

And it's worth pointing out, that before it's claimed that it just means "Trans Rights Activist" and is a neutral descriptor, most trans people aren't activists, but it's still a term that's leveled against all of us indiscriminately. There's spite and hatred behind it.