But…it is. Language isn’t precise

Sure, maybe I was being too strong there by saying it's not a thing. People do use it. But I would be cautious of using it yourself unless someone tells you specifically that they want to be referred that way.

Approaching someone who would be willing to accept - without being able to give a real answer - relies on them having faith

It really doesn't. It relies on them not being an asshole. And not making generalizations. The intricacies don't matter on a day to day level of interacting with people who you're not intimately familiar with. Treat them as you would any other person of the gender that they're presenting as. That's literally all there is to it. Anything more is personal preference to the individual, just like it would be for any non trans person. Do you need to understand the intricacies of tomboy vs butch to interact with a woman wearing pants? No? Then you don't need the same level of detail for trans people either.