I'm not sure I agree with this exactly. It's a fine line. When my son plays...
Moreover, it is a *tendency*. It may be, in aggregate, over several instances of play in the long term, boys will spend more time 3rd person and girls more time 1st person. This does not speak to specific times or specific individuals. It doesn't mean no boys ever do 1st person, or that none of them ever drift from one PoV to another.
A toy sold to the masses is generally going to be built to the law of averages, not to the anecdote, so to speak.