Yep, them and bittrex required a working blockchain for the coin. And of course safex still has a working blockchain - the BTC blockchain since safex and a number of other coins on these exchanges use the omni-protocol
And unfortunately some/many still do.
For a very long time now, safex was going to be on its own blockchain. And the bluepaper only shows how it is to be done, not that it was going to be done since that has been known for a year or so.