I've said this many time but I'll say it again. The way the upfront 3 works in the system DS was playing previously (4-3-3) the front 3 were interchangeable. I think DS and the recruitment team would have looked at the 6-7 players they had to fill those three spots (Wes, Kod, Davis, Jota, ElGhazi, Trez, Jack) and thought they had enough. No doubt DS would have preferred more cover because, as you say, none of those players have played in this league before.
For me I think this is a real shame for Davis, he could be getting an extended run in the team right now if he was fit. I do fear injuries might mean we never see the best of him.