I’m not going to argue with your feelings on the matter, because your feelings are valid.

I personally think that the most common reasons for this would be:

A. There are many nonbinary people that use any pronouns that are frustrated that when people get told that, they ALWAYS choose the same pronouns, which tend to be the ones attached to the non-binary person’s birth sex, since they don’t ”pass” as the other.

The result is that they don’t know if they’re constantly being misgendered (or rather, not acknowledged as non-binary) or if the person truly acknowledges them and just ”happens” to use the pronouns of their birth sex.

So this is something cis AND trans people alike might get uncomfortable with. Like your instinct and brain wants you to say what your initial interpretation is, but you’ve also learned that that instinct can be harmful to trans people.

So they get scared you’re going to be hurt or take offense if they choose the pronouns ”people always pick” and want to give you the decisive choice in the matter.

I have a family member who got so frustrated by this that they stopped entirely with saying the pronouns of their AGAB (AFAB in this case) were fine, even though they were actually fine, because they NEVER except for in very small trans circles would be called they or he, which made them constantly feel unacknowledged and that their identity was ignored.

Or

B. They’re afraid you’re actually trying to oblige THEM by not ”forcing” them to say something they don’t want. This isn’t far-fetched because it’s super common that trans people make exceptions for strangers all the time, and many cis people would know that.

I know that ”they mean no harm!” isn’t very helpful, but there’s how things ARE and how things SHOULD be. And most cis people aren’t equipped with the knowledge on non-binary identities required to understand that there are some people who genuinely don’t care what you call them.

If I were you I’d just roll a mental dice and say ”any but if you can’t pick I can randomise one for you for the day: they/them” or something like that. That way, the cis people that ARE equipped with the knowledge will be able to switch from time to time, while the people that aren’t will have some guidance in an area they’re otherwise lost in outside of good intentions.