People really piss me off.
This is the simplest answer. You're probably wondering why & how they did that enough to make me stop calling myself "trans", though. There's a number of weird people (even nonbinary people) who try to rebinarize other nonbinary people as transmasc or transfem. They pull an odd "oh, it's not a gender but a population descriptor and you can only masculinize or feminize" card. It's not a gender, sure, but respect some people don't want to be grouped with people in a way that is misleading.
So, yeah, if you're a cis woman who gets a mastectomy for health reasons then you're transmasc. Congrats! Yeah, I didn't know that either until someone tried to define mastectomies as masculinizing in contrast to feminizing augmentations when explaining why you can only masculinize (be transmasc) or feminize (be transfem) based on agab. All while assuming I even want a mastectomy and not a fucking radical reduction at most and 6 realistic tummy nipple tattoos.
It's not very apparent in selfies (angles + makeup a lot of the time) but I manage to pass as a man already in meat space without doing much. Transphobic & intersexist slurs were thrown at me through high school as a result. I'm not on t. I'm intersex. I grow facial hair. I do not want to actually masculinize myself more. If I go on t, I am only going on it for voice & bottom growth reasons (TWO THINGS THE DAMNED VARIANT I HAVE DIDN'T GIVE ME, FUCK) and then going off of it.
I need more feminizing procedures to actually make myself properly as androgynous as I want. I'm a weird kind so it's not ideal, still dysphoric, but I am far more okay with being misinterpreted as a woman than as a man. Though I'd much rather be seen and interpreted as a female dog (unachievable but unforunate human bodies can be made androgynous which all dogs are). No, I will not call myself "transfem" either. Even if I could use that term, that would still be an unacceptable binarization.
So I'm not calling myself "trans" anymore. If transness means I have to rebinarize my perfect, intersex + nonbinary self than fuck you. I'll opt out of "picking one" AND transness. I am a simple xeminine/neofeminine demibitch dyke who uses it/she pronouns and that's all. Still cisn't, just not playing your dumb exorsexist (and intersexist) games.
Oh, and I forgot to ask that one person but I should have. Is getting genital nullification surgery transfem or transmasc? I don't want it myself. I'm neutral on having a vagina specifically. But really, would that not be transneutral which just minutes ago, they said isn't a thing? Hmmmmm. The binary categories aren't very strong.