In the original pre-Disney illustrations, Christopher Robin looked quite like a girl. He had longish hair in a page-boy cut, and he wore a sort of blouse. He looked like the little boy of a woman who wanted a little girl instead and tried to turn him into one.
You have to remember the time of the original stories, which was the 1920's. Children did not dress as they do now.
"In the original pre-Disney illustrations, Christopher Robin looked quite like a girl."
That was the style among those Victorian/Edwardian artists. Actually, POOH was written later (in the 1920s, I believe), but styles don't change overnight.