Hmm. Maybe it was later then. I had seen the slashdot.org post and tried it out, dabbled with it. I didn't take any of it seriously. I'm fairly certain that there was a seed phrase but I can't be absolutely certain. A bunch of random words then?
There are wallets that used mnemonic seed even before BIP39 was introduced. But it's certainly
not Bitcoin Core.
Electrum for example had their own seed words implementation and 1.8.1 was released on Aug 2013(?). IDK the exact date and the older version's dates.