Yeah it's a little odd to me. Technically, every specialist blockchain + UI pairing could be considered a dapp too, but it looks like their focus is on platforms on which you can run smart contracts, a truly decentralized hosting of code that anyone can run and verify. Does that make sense? Who knows.
Interesting stats from the Sincerety API though. The post count for steempress is surprisingly high. Is that a lot of spam being forwarded?