I think the difference here is that a DPoS blockchain means that all blocks are created through delegation.

DWP seeks to create superblocks and only superblocks through a process that is similar, yet still a bit different, to a DPoS blockchain such as graphene. The main take away is that the Gridcoin blockchain will remain a PoS blockchain if DWP is implemented.

Really, it will be a combination of PoS and dynamic selection (DPoS... sort of) which is an entirely novel idea by my understanding.