You can hatch those pullet eggs but there is a good reason people recommend you don't. You usually do not get good hatch rates for different reasons.
An egg needs to be put together about perfectly to hatch. The egg laying process is pretty complicated. You may have read on here how it is not unusual for a pullets first few eggs to be thin-shelled, no shells, really thick shells, double yolked, no yolk, no whites, or misshapen. That's just the things you readily see. There are other things about putting an egg together correctly so it will hatch that you don't see. It can take a while for the pullet to get all these bugs to her egg laying process worked out. To me it is amazing how many actually get it right to start with.
Also a pullet's first eggs are usually pretty small. They get bigger the longer she lays. Those small first eggs don't have a lot of nutrients and there is not enough room in the egg anyway for a decent sized chick to hatch.
I've also had the problem that a pullet just starting to lay may not have her eggs fertilized. She has not always matured to the point that she and the rooster are on the same page as far as cooperating to fertilize the eggs.
I have hatched pullet eggs. I've found that my hatch rate is usually not as good if I wait until the eggs are larger. Most of the chicks that do hatch live and grow but I'm more likely for a chick to die if it is hatched from one of those small pullet eggs than if I wait.
I've found that if I wait until the pullet has been laying eggs for at least a month most of these problems go away or are at least greatly reduced.