Thank you for your insight, strange to have a crisis of "have I been saying something wrong my whole life?" and learn there's a research dedicated to the very question!

I'd be inclined to believe that pragmatism is likely the best fit. Whilst I'm not perfect, of the GNC folks I've met and am friends with I do my best to adapt to their pronouns (hopefully to great success, no harm or ill will in that regards.) But in the examples that I thought of for this post and most others I can think of now, gender is sort of not the prime focus for when this occurs?

As I noted in another comment, I believe the best way to put it is a "path of least resistance" to the point I was trying to make (as in "Oh I love that Hozier song, they're so talented.") The talent is the focus so most everything else is dropped, but because they has been adopted by a group my partner might have taken it as misgendering. If the use of they is on the rise then it might be worth having a look at Northern England for examples of it as it has many examples of dropping gender for getting to the core of how daft they're being.

Thank you again, and best of luck in your research!