Well, I don't understand your problem.
technically speaking, the pool (which is more or less probably based on a server software AND a client (aka Wallet)), the exchange website and the wallet that manages deposits/withdrawals are 3 (or rather more) different things.
That the wallet that contains the website's DEM deposits is still online, up to date, AND contains funds is probably pure luck.
Maybe there are more coin clients on coinex still working correctly, but who wants to try out, which ones?
Without maintenance, also DEM will become non-functional in time.
If the breakdown of coinex is really, as many people suggest, a scam scheme, someone overlooked at least this coin-if it is (as I tend to think) just a bundle of coin clients slowly dying of maintenance problems) DEM is probably the only client still running stable on the connected machine, without being offline, not running or being on a forked chain.
When no one is mining on a pool website, this doesn't mean anything for the connected exchange website, nor does it imply that pool and exchange rely on the same clients or even are on the same (virtual) machine.
Pure luck, IMHO, that the connected DEM wallet is running, online, not forked, still connected to the exchange website AND containing coins.
If you have funds on coinex and rather don't believe this and wait for the website to finally die completely instead of taking the hint that you might salvage some value, go ahead, I'm happy I lost only SOME and tried to help other ppl to do the same.
It has been postulated that the DEM hot and exchange wallets are indeed linked to the mining pool outputs... you can trace it on the blockchain. At one point, DEM died here and someone put it back online.