You are refreshingly not confused, only think you are .
There are no DPP LNBs. DishPro Plus is a switching method, an extension that takes 1 or 2 DishPro stacked signals, does band-translation and restacks them on a single output run to a Separator behind a dual-tuner receiver.
DP and DP Plus switches must be fed by DP LNBs. Often these are combined in one assembly as with the DPP Twin (2 DP LNBs + DPP switch) and Dish 1000.2/1000.4 (3 DP LNBs + DPP switch).
Thanks for that explanation. Now I've got it.