Earlier quoted context omitted.
There's also a similar theory to explain why boys are more interested in cars than girls (which my kids have proven convincingly, albeit with a low sample size): boys, as future hunters, are attracted to preys that move, hence, in the modern environment, to balls and cars.
Are you perhaps discounting the societal influences pushing your kids towards their respective interests? If they view any amount of advertising or interact with other children who do, for example, they could already have ideas about what is "appropriate" for them to like.
All I want to say is that there seems to be a stupid amount of aggression towards even the mere idea that statistically girls/boys might like something other than boys/girls do even if social conditioning were completely removed(which is a nonsensical idea in the first place, a child is a member of the society from the second they are born, they are not goldfish).