The speaker says grandmasters have extensive chess practice, while O3 may have had no chess games in its training data; he notes that O3's training process is not known to him.

“also they've”

“trained on it a lot like they've done lots of that and whereas o3 possible i don't know that we don't know the details of o3's training process but it's possible that there was not a single playing of a game of chess at all in the training process”