If they do not they are not breeding Ameraucanas.
I should restate that - if they have any straight comb chicks, the parent stock were not Ameraucanas.
You can get straight combed crosses. When I breed my Penedesenca rooster and ameraucana or U of A hens I get 50 / 50 straight and pea combed. If they send straight combed chicks they could not tell you they would be olive eggers. I had a few Barnevelder x ameraucana straight combs lay olive but that is not the normI don't think that is necessarily true. Most chicks will get the pea comb from the Ameraucana, while some chicks could possibly get the straight comb from the Marans. But I have never raised Amerauncana so I don't know first hand what happens when they are bred with other breeds.