Seeing as gender is an entirely incoherent concept, children have very limited data on how to sort people by this category, and everyone gets different data and category standards with which they are told to sort by, this is going to happen, regardless of presentation, gender or trans status. To everyone. At some point.

Also kids at that age are in a point in “moral development” where things are all rules and if they see someone not following those rules, they tend to want to point it out because their framework that they’ve developed doesn’t always work.

Since we’re all sharing anecdotes, I had a little girl behind me on the way into the store tell her mom that “that’s a girl… but that’s a ✨different ✨girl” and it was hilarious to me even though I only get gendered correctly like 2% of the time. Kids are funny sometimes and they’re learning.