What is a typical boy?

A phrase like this always stops me.

Whenever I read something like this I imagine what it would be like to read it if you were a boy and, for instance, you were shy and bookish.

Or gay or nonbinary.

It seems to assume that there is a set of behaviors that define being "typical" and that if you don't do these things you're -- atypical? Abnormal? Not a real boy?