This is a very interesting observation with regard to very old wallets. There are groups whom are claiming that they can organize a crowd that will be able to steal Bitcoin by guessing the private key but as it turns out nobody is moving the SATS into mixers apparently. If somebody guessed the private key then that will be their next move and then make it seem that they stole the SATS. But from the looks of it, it was moved by a veteran whom was keeping his or her stash for longest time and then moving it cleverly but as if a veteran for the first time after almost 11 years of successfully securing the keys.