I've had this conversation with my non-binary child. They point out that if you don't know, you should say they/them, and when identified, absolutely use the identified pronouns. This was actually part of us getting their teacher to understand - she is very strongly female and as such would be offended by any pronouns other than she/her.

The only people who should know your physical gender should be a medical professional, and that will include EMTs and those who run blood drives.

The problem becomes when, as with both my child and the LW, when the pronouns can change on an apparently-random basis and they/them doesn't always fit. If everyone defaults to they/them, perhaps it doesn't matter as much.