The only other explanation would be if he only had one wallet from the early days (I find this implausable for someone developing the very fist blockchain coin with testnets and then production testing etc) and had inadvertently lost/forgotten the passphrase.
The original wallet implementation did not have a passphrase (in fact that wasn't added until after Satoshi had disappeared from memory).
Ah! Would that wallet.dat work with the latest iteration of Bitcoin Core or at least be able to 'upgrade' so it could using progressive versions of the core?
Also if Wright has all of Kleiman's BTC stuff on a pen drive then this still further cast into doubt not only Wright's claims but also those claiming that Kleiman was 'Satoshi'.