tl;dr version: Did Gox allow preferred clients to keep shared private keys to BTC on the exchange, which allowed them to independently move their funds out?
I do not know. However, if Gox did make that accommodation, then it would be smart for any such clients to expeditiously move their funds to wallets that Gox holds no control over, as soon as they learned of any financial troubles or probable failure of Gox.
If such 'whales' were not willing to trust Gox sufficiently to deposit their BTC with Gox in a manner that they would lose all direct control over them, then for sure they should not trust Gox now not to yank the coins out of the shared wallet into a Gox trustee-controlled wallet, in order to pay other creditors and fund Gox's rehabiliation.