Nitpick: The early moves in the game are called fuseki. Joseki refers to well-studied local patterns of moves and they appear through the middle game, not just in the early game.
A couple of things I love about go is that you don't need to memorize fuseki, and that applying joseki correctly is as much a matter of judgment as it is of memory.
(I am a 1 dan go player but haven't played much in the last 15 years.)
He could be thinking of shogi (though the kanji is 定跡 where joseki from go is 定石), where joseki refers to the well studied ways to play the opening of the game.