Gibby doesn't do everything he can to win each and every game. He makes decisions for the long term health of the team, as he should. I think refusing to allow Martin anywhere near dickey is one of these long term decisions.
The reason I bring up the 17th inning of a wildcard game is because in the potential last inning of the year there are no longer any long term considerations (except serious injury) - and we can truly see what Gibby thinks is the best move to win the game at hand.
So the question is really asking: does Gibby actually believe we have a better chance to win the current game with Thole catching, or is he just trying to keep Martin happy for the long term good of the team?