If the kid makes up the rules, then the kid can change the rules. They can't do that in the real world, they have to adapt to the environment they find themselves in, and develop strategies that work within it.
Ah, in my opinion the world needs more people who are willing and able not just to follow the rules, but to imagine what it would be like with entirely different rules.
If you think into your memory bank of childhood life, you may recall when kids engage in fantasy play they are in a constant dialogue with each other and with their environment. It is a process.
