He meant to say, I think, that there are fundamental differences between the genders and these are significant things. Leaving aside the fact that feminism was never about making women and men the same, I agree. Many times while rearing children I wanted to believe that boys and girls were exactly alike, predictably alike, but it isn't true. It makes for certain predictions. Boys like to carry around long, stiff objects and poke, stab and pretend to shoot projectiles at people with them.
Girls hide things in dark places, like drawers and boxes and mother's purse.
For the most part, though, boys and girls are a lot alike, especially to parents. Given time and space, they will all run wildly without purpose and suddenly fall down in a heap. They will climb, trip over and crawl under things before they go around. Kids all eat large quantities of food, sleep vast lengths of time in filthy bedrooms while surrounded by stuffed animals, avoid brushing their teeth, stink and refuse to bathe, then stand under a shower and use up all the hot water. They will run across the street without looking.