I'm pretty sure they mean that they are using Merkle DAGs. A blockchain is a Merkle DAG. The proof-of-work algorithm in Bitcoin is an algorithm for deciding how a node gets added to the blockchain. Depending on how you look at it, that algorithm is not part of what makes it a "blockchain".
Admittedly people are sloppy about how they use the term "blockchain". I would prefer that people use the term Merkle DAG and forget the term "blockchain" altogether, but I think we are stuck with "blockchain" ;-)
"People" are also sloppy about how they use the term "cloud", yet the world goes on with that concept in hand applying it to everything in site, often times in irritating ways. "Blockchain" is now a thing people can hold in their hand as a way to visualize the concept of a nearly immutable data store. That idea of storing something in an immutable way represents a shift in the way we can think about system's design. Calling it a "Merkle DAG" isn't going to kick off that insight any better than using "blockchain", but remembering what it really is and drawing the distinction with the right people can be immensely useful when trying to implement the insight.
Admittedly people are sloppy about how they use the term "blockchain". I would prefer that people use the term Merkle DAG and forget the term "blockchain" altogether, but I think we are stuck with "blockchain" ;-)