Some frizz cochins do have a little tuft, but you are right: these guys' is rather pronounced. I suppose they could be missing the extra toe if there was silkie in the background, but I kindof doubt it. SOME silkie trait ould have made it through: dark sin, the comb, toe, something. Even my 1/4 silkie frizzle had extra toes.
I have chicks I have hatched from the same Silkie/Cochin parents. Some look more like Cochins and some more like Silkies. Out of four that hatched the first time, I have two with 5 toes and 2 with 4 toes. Same parents. The 5-toed birds definitely look more like Silkies now that they are grown. They others definitely look more like Cochins. I think you can get a mix of both breeds. Don't you just love Frizzles???