Yeah that sounds pretty snake oily to me. For me even if they are the real thing I don't like the idea of the breeding process, if inseminated i'd feel better about it, but a chicken covering a quail isn't something I'm interested in seeing or promoting.
Should anyone reading this thread...
Personally I would avoid it. The reason being is that the seller is saying that the breeding happens by natural process, the only proven coturnix-chicken hybirds I have seen have been inseminated. All he has to do is not guarantee the hatch due to shipping concerns and send you any old coturnix...