Yes, it's totally the same Ben, returning clients money versus aplying a haircut to ETH(100%), BTC(15%) and LTC(35%).
They haven't said they will return clients "money", they haven't said they will return ANYTHING yet specifically. So again your example fails.
That is a good point though, the ONLY thing Cryptopia didn't do that DragonEx did is say
"DragonEx will take the responsibility no matter what."
This early they can't guarantee that, Dragonex says it will take responsibility no matter what - which is a silly thing to do because liability may be elsewhere.
You have a good point that DragonEx can't guarantee anything at that point, unless they already know the exact extend of the damage.
However in such cases, the liability is surely not upon one's customers! Unless an exchange is sharing their earnings with their customers, they can't share just their damages.