I've never had any problems with them eating it. I think they call it layer crumble because it's formulated for laying hens and has most of the nutrients they need while laying (protein, calcium).
i have heard because of the calcium that it is hard on their kidneys. i feed a 17% grower and free choice oyster shell then hens.....roosters.....and chicks can all eat it. When the hens need the calcium they will eat the oyster shell as needed. Lots feed the layer and never think twice.....so it really is up to each person.
This question has been asked for years and some say the calcium in layer will damage rooster's kidneys, but many people feed without any problems. Majority use Flock Raiser and free choice oyster shell in their mixed flocks.