With males, they can breed once they are ready. They don't have to carry the litter and have that stress on their body. Younger males might not fully know what to do or be interested in a female, some might not be fertile yet. One reason to wait is to see how they develop. Young rabbits can be hard to judge as they change a lot as they grow. If you are breeding to the breed standard, you would want the offspring to meet the standard and that is hard of the parents have more serious faults. If you know what faults the parents have, it is easier to compensate for them by breeding to a rabbit that is better in that area.
There really is no rush to breed a male. I would suggest waiting to see how he develops before you breed him.