Hmmmm, call me cynical but I see an out here. They could still dispose of in humane ways and still be in compliance with their statement (and that's quite subjective though I will say I think there
is a legitimate distinction to be made).
Hey, there's a LOT I don't know about hatching eggs and just how precise they can be in getting exactly how many chicks they need, and actually selling all of them. But if they sell every single hatched chick I'll eat my hat!
That said, I'm sure they try to get it as close as possible, for economic reasons if nothing else. It costs money to run incubators for eggs that won't produce salable chicks.