The overwhelming experience of parents is that individual children have strong preferences for certain kinds of toys, and that aside from a certain amount of overlap, these preferences tend to fall along gender stereotypes.
That's not a politically correct idea, so people have spent time studying the idea, sure there must be some parental bias involved, and in some cases have found it. They've also found ample evidence of certain children that don't meet the stereotypes. However, it would be very difficult to find evidence that were children to grow up completely devoid of parental and peer influence on toy choice, that they wouldn't tend to develop toy preferences along gender stereotypes. In fact, there are a lot of stories of parents who actively promoted cross-gender toys, and who were frustrated when their children nevertheless developed strong preferences for gender-typical toys.
For my own children, my eldest daughter was showered with "girly" gifts and plays with none of them. She likes toys that make funny noises and music, and have blinky lights. She has cerebral palsy and some autistic characteristics, so that may be a factor in her toy preferences. When she spends time in the hospital, people give her more dolls and stuffed toys. Aside from a brief stint with a Barbie doll she called "Darby," she hasn't liked any of them.
So our second child, a son, comes along. Since our first child did not like gender-typical toys, we assumed he would be the same. Not so. Despite living in a house full of girly toys, he too didn't like any of them. He gravitated to the few cars we had in the mix, and turned duplo blocks into guns, swords, robots, and cars. He was strongly influenced by his cousins, whom he sees around once per month.
When our third child, a daughter, came along, we had forgotten about how many girly toys we still had lying around the house, but she took to those like a moth to a flame. There are toys she plays with her brother: building toys, games, and balls. But when she plays by herself, she uses the stereotypical female toys. Her brother occasionally will play dolls with his sister, but when he plays by himself, it's with stereotypical male toys.
Now if a sociologist came into our house and studied toy preferences, she would see a parental bias. They would say our boy plays with cars because that's what we buy for him, and our youngest plays with dolls because that's what we buy for her. However, we know that we buy that way because that is their preference, not the other way around. The preferences came first and we only support them. Many parents who started out priding themselves on their political correctness uncomfortably find themselves in that position.