I believe that's why it's considered a white hat hack.
The hero wipes all records of their actions by blindly sending it to Bittrex; putting the burden on them to 'do the right thing' and return the stolen funds to the owners.
If it was sent to a personal account or specific account via memo, the funds would be a lot easier to trace and freeze if requested by regulators/officials for whatever reason. Given that they now fall into an exchange pool, it's up to @Bittrex to distribute accordingly or risk their reputation.
I think they will do the right thing, even if only to appease the community and shine again as the top Hive exchange.
If Biitrex does the right thing than that will great, but seeing the history of so many exchanges which are great freinds of our Sun, I doubt Bittrex will do the right thing