If I were operating bitblender and knew LE was coming soon, I'd wipe the servers erasing everything including the BTC private keys. Of course LE has been sending coins through bitblender so they know the addresses where all the incoming deposits were aggregated. So if they catch you with those keys, they can prove you are the operator. Or if they catch you with the secret Tor uses to identify bitblendervrfkzr. So I expect the operator no longer knows those secrets, and hence can't bring bitblendervrfkzr back up and can't send your coins anywhere. If so, the coins have been destroyed.
It makes no sense to destroy private keys at all. If the funds were kept in a LE-"unsecure environment" he could, as you suggested, move all the coins to a new adress he generated somewhere safely/offline, then destroy/remove the server in which the "unsecure" keys and adresses were stored, and still keep the funds.
Then he could either mix those funds using coinjoin, wasabi, monero, chipmixer, or simply wait until a provably-fair "privacy"-provider mixer comes into the market.