I don't find that true at all. We hatch hundreds of eggs every week. Breed does make a difference. Our Wyandottes hatch no matter what conditions you put them in but our BCM don't. They also take longer to hatch.The BC Marans are no different than any other chicken egg. I have hatched several thousand of them . This week had 11 out of 13 hatch . Most people do not know how to set an incubator up to begin with.