I think if we feed only in the am and afternoon, they can reach breeding age. However, there will be different types of mixed combinations spread between A, B, C and D. The trick is to find the right pairing from those to produce broilers.The classic CX is a hybrid, yes. Not a true breed.
Even the Cornish moves her @$$, which is good for her. (Oh, took about 7 months before she started laying)