It's difficult to look at LEGEND and not see TOM CRUISE in it, but, I mean, my point is that he wasn't nearly so annoying or powerful or crazed 20+ years ago...
Because he was still green in the business...
Wouldn't it then make sense for all of the non-human characters to refer to them as 'boy' and 'girl' just as you or I might use 'bull' or 'cow'? I.e. whenever someone said 'boy' they were in effect saying 'male human'.
I'd go along with that as an explanation too.