Calling a girl "boyish" does seem to have a different level of impact than calling a boy "girlish." But I've also heard "guyish" and "typical man" used to mean

Calling a girl "boyish" does seem to have a different level of impact than calling a boy "girlish." But I've also heard "guyish" and "typical man" used to mean boorish, lazy or stupid. "Typical woman" creates about the same level of offense in that case, and has equally well established definitions. I suspect at the end of the day, this form of sexism probably balances out in both directions, but with clear bias in specific cases depending on the audience.