Well, it's a bit weird. They won't let you book DL W/S classes on AF/KL metal over the Atlantic, but they will book DL W/S classes on AF/KL short-haul intra-Europe flights (which just book into Economy cabin) when combined with DL metal over the Atlantic booked into C+ (W/S) classes. You'd expect these to book into coach classes (just like F fares which include a segment on CRJ-200 equipment domestically), but it doesn't for whatever reason and it is likely confusing system.