My guess is that he/she destroyed the private keys to those addresses
Although I agree that it is unlikely Satoshi will ever move his coins, and it becomes less likely as time goes on, I would disagree with the quoted statement. I think it is unlikely that Satoshi destroyed those private keys given his previous statements on such a matter:
Sigh... why delete a wallet instead of moving it aside and keeping the old copy just in case? You should never delete a wallet.