They recommend that you switch to the layer feed when they are around 18 weeks or so, regardless of whether they are laying or not.
They need the calcium in order to lay eggs properly and have the hard shells.
It doesn't matter if its layer pellets or layer crumbles.
Obviously if you still have a bag left over when they hit 18 weeks you would continue to use it up and then switch.
I bought the layer pellets and one of my flocks hated them and wouldn't eat them and the other flock was fine with them.
I never bought them again, I like the layer crumbles better.
Both flocks will eat them, and I have no waste at all.
Mine never scratch them out of their feeder, if they did maybe I would feel differently.
Another reason I like the layer crumbles is that they pull double duty and can be used for hot mash on those cold mornings.
I don't know about crushing up the pellets, I mean if you wanted to spend a while smashing them with a hammer or something I guess you could, but it doesn't guarantee that they will eat them even then.
While both the pellets and the crumbles have the same nutritional requirements, they may taste different. They are a different color and the pellets may have something added to mold their shape. Maybe, maybe not just wondering.