The Grandmaster follows the rules. The Grandmaster uses experience and logic to predict the future board-states 3 or 4 turns ahead. This information restricts their options. The Grandmaster is a "best move" robot.

The novice is free to move anywhere or do anything they think of. The novice is not restricted by the rules of the game or by the potential future board-states. The novice is FREE.

You suggest that the Grandmaster is "free" to (EITHER) choose their best move (OR) some other move.

But why would the Grandmaster ever choose a move that wasn't (to the best of their knowledge) their best move?

Are you suggesting there is some utility in knowingly "choosing" a bad move?

I mean, if the Grandmaster was training an initiate, they might make moves that would best train their partner, and not necessarily the best move to win the game as quickly as possible, but that would still be their best move, BASED ON THEIR GOAL OR MOTIVE.

You must always make your best move (unless you are knowingly self-sabotaging).