I don’t think gender matters much at that age. It’s an age of exploration. What’s a toddler boy, toddler girl, toddler trans boy, toddler trans girl? Not so different at all. If a kid’s got preferences, allow it.
The drip drip drip of major sexual differentiating doesn’t start ’til about age 8 that leads to puberty.
That’s also why I don’t have any issue with hormone blockers. It allows for time.