They/them has always been the way to refer to someone whose gender you don't know. It is the neutral term between binary ones. So, if they don't know or are unsure which binary pronouns to use then I think it's a positive.
As for correcting someone, I think it's fine to do that. If the person in question continues to use the wrong pronouns after correcting, that's when I might actually consider it misgendering, unless they're just super ADHD like me, and then it's possible it might take a second reminder, LOL.
For reference, I'm technically a trans-woman though I'm agender, I present femme and prefer she or they.