It is not the same situation as with "poloniex" account!
The difference is on the date the owner keys are updated.
The "poloniex" owner keys changed yesterday the "c-cex" just created from steemit on 8 April (like "poloniex") and since then no activity...
The founders created/reserved in purpose as much exchange-names as possible back on 8 April to be sure they get not taken away from individuals that have no connection with the particular exchanges... And have already stated back then that they will give them to the interested exchanges... So only "exchange" account's that lately have changed their "owner" keys are real candidates for steemit adoption! ;)