Yes I understand it is a breeder that has decided this and I'm sure he's not running 60 horses either. I know of a ranch that breeds high quality quarter horses that doesn't breed their two year olds.
Its an opinion that he shouldn't be breeding such young horses. That is all. Like I said if he wants to breed unproven young horses more power to him. Even better if he gets good money for them.
I've seen backyard breeders with 40+ horses.