I'm one of them. Grew up with "they" as strictly plural. Had enough red ink on school essays that the lesson sank in. Every time I see "they" in a singular context it's like mentally stubbing my toe on a tree root. I have to stop, go back and re-read to be sure I didn't miss something that set up the plural context.

If you insist on being gender-neutral, you have to write "he or she" which quicky gets tiresome. Or rewrite without using pronouns, which can also be awkward.

I learned that "he" is gender-neutral if there is no other context, and that's the way I continue to write.