Optimal play includes bluffing. It's "optimal" according to game theory.
For example, game theory may tell you that in a particular situation, you can't be exploited if you bluff 10% of the time. If the opponent bluffs less than that, you can come out ahead by more often folding when he bets. If the opponent bluffs more than 10%, you can call or reraise when he bets. But if he bluffs the optimal amount, it doesn't matter either way, you can't take advantage of him.
So this bot would bluff at 10% to avoid getting exploited, but wouldn't try to detect whether the opponent is exploitable. (The latter is risky since a crafty opponent can switch up strategies, manipulating you into playing an exploitable strategy.)