This is very true! I've always had a mixture of hatchery layers, and non hatchery. My marans, non hatchery, always drove me crazy because they wouldn't lay until 40+ weeksEight months doesn't sound far-fetched to me. I don't know about AM in particular, but non-hatchery stock of most any breed will generally lay later than hatchery stock. This is true for Brahmas for sure. Also depends on the time of year they come of age too IMO.
See, I don't have time to try to sell roosters. I give almost all mine away, unless it's just one that I'm not stretching to house and feed. When I have boys in bulk, it's a free-for-all. It's SO much easier!