If your point is, well, this is just two little girls, you're right, that alone would not allow one to extrapolate to all little girls everywhere. However, I know for a fact that large companies and institutions have already done lots of experiments with kids (especially companies that have a vested interest in figuring out exactly what kids want, in order to maximize their profit) and my understanding is that the studies show that yes, girls mostly prefer to play with girlish things and boys with boyish things. This was the result of Science with a capital S. Now, do all boys hate dolls and all girls hate robots and dump trucks and guns? Of course not. But in the majority of cases that's how the cookie crumbled in the real world.
Also the whole "pink vs blue" thing you see in stores in the kid sections? Do you think that's some conspiracy or cultural artifact? From what I've heard, it's isn't. They've done experiments. Girls in general, world-wide, really do tend to prefer pink and boys prefer blue. In the general case, when dealing with large enough numbers, etc.