"Boys and Girls" isn't Inclusive?

I was reviewing the Wikipedia entries for The Wiggles and their members (something had sparked my curiosity to do so; a clue on Jeopardy I think). One statement on Jeff Fatt's page left me scratching my head. "Fatt reports that it took twelve months to "learn the language of preschool", including addressing children using the inclusive "everybody", instead of "boys and girls", and that The Wiggles' first performances were traumatic for him because he was not used to being around children." I've highlighted the part I don't understand! Is not 'everybody' either a boy, or a girl? And how is "boys & girls" less 'inclusive'? They're not cows or dogs or rocks, they ARE boys and girls, who's excluded? Is there some context I'm missing?