I think you missed this:
As I said we know how and where the USD moved, so yes.
They know to whom the funds have been transferred.
Where does not equal whom. We have no idea what method of withdrawal was used for the USD, but it';s unlikely that the hacker tried to get it payed into their bank account.
While unlikely, we don't know it. Keep in mind, that all those more or less anonymous withdraws take weeks, so either MtGox helped to speed this up, in which case they very much know with whom they dealt, or yes it was redrawn to some bank account.
Or it was transferred to a handful of throw away account w/ fake info and used to buy BTC and removed from the site.
Or it was transferred to Accrum Exchange and used to buy Liberty Reserve.
Lots of methods to get USD off MtGox nearly instantly. Not all of them are low cost but I doubt any thief was worried about that.
The idea that the thief did a wire transfer to their personal bank account is just stupid.