Gender bias and gender identity are two very different things.
I believe there are appropriate topics around gender bias that can be taught at an early aged. Gender identity, a big no.
As far as bias, I think there is a balance between letting kids be kids and teaching them things. Things that promote girls (future women) to dream big and be anything they want is a good thing. I recall years ago being confused when I first heard the many of the great chefs in the world were men. Same thing when I first heard about a male nurse.
On the flip side, its ok to believe girls have cooites up until a certain point.