but why would you call me a TERF, hypothetically?

Given our short conversation thus far, I don't see a reason to. The term is almost always used disparagingly, and I'd rather not be blatantly disrespectful to people I don't even know on the internet.

I do not think most GC individuals are able to be classified as "TERFs" because most GC individuals aren't really transphobic, at least from my interactions with them.

That being said, I think that (occasionally) some GC folks fall back on or use transphobic rhetoric and fear-mongering, in which case I would refer to those specific individuals as transphobic, and therefore "TERFs". Basically, not all rectangles (GC) are squares (transphobes).

using "woman" to refer to females would be the courtesy

I suppose I agree. Generally, I refer to both natal and trans women as women, as a courtesy and also as part of my understanding of gender (which we probably have disagreements on). I more so meant "natal" as a replacement for "cisgender" as I understand not all natal women identify with that label (rejection of gender identity conceptually, the term's associations with stereotypes/conformity). Usually, I only do this when I'm clarifying whether I'm referring to the category of natal women, or trans women.

Arguably even calling you a trans woman is a courtesy, rather than a transman or transmale.

This gets complicated and we probably disagree fundamentally on some specific terminology and ideas here, though as I mentioned, I don't demand anyone call me a certain thing if they don't want to. I do think it's a kind thing to do (to use preferred pronouns, refer to someone as the gender that they identify as), but I don't necessarily think it's disrespectful, if that makes any sense.

Although, if we're being technical, I would even simultaneously call myself a transsexual male and a transgender woman.