The point is, you don’t know — no one knows — so why have an opinion on it at all?
Turner syndrome, Kleinfelter’s, XYY mutations, and androgen insensitivity syndrome would all like to have a word with your facile categorization of sex.
You never did bother answering why we can even say a boy likes “girlie” things if, by your tautological definition of gender, anything a male likes should automatically be considered “boyish” (and vice versa), but hopefully you’ll take five seconds to think it through instead of knee-jerk reacting to me.
I could say gender is based on societal expectations and sex is chromosomal all day, but I think it’d be easier if I asked you to just reread this post once a day until you decide to read an actual biology textbook.
I can guarantee none of them were written by Orwell.
Have a nice day.