I think there is a (small!) bit of a valid point here in that nobody really claims PoW blockchains scale well (okay maybe the extreme big blocker faction?). PoW is trying to do something (permissionless system, nodes on non-dedicated hardware, objective global consensus, etc.) that isn't really focused on scaling as a primary design goal.
However, by contrast DPoS is very much built around a premise of scaling and projects (and Graphene in particular) have a history of making extreme claims about scalability (such as 100K TPS or higher, claims of being able to support Reddit-scale in the Steem white paper, etc.) which are often narrowly made to the point of being misleading IMO.
CPU-wise it might be valid to throw around these bold claims, but can you imagine how fast the blockchain would grow and how unmanageable it would quickly (!) become if someone actually tried to do this? (Not to mention other issues such as bandwidth, etc.)
So measured against the claims, I think it is fair to say that DPoS has more scaling 'problems' because its claims and ambitions are much higher.
I agree with this.