The only way to order AI to disarm a mine is to point at it and use tilde quick menu, while AI can be ordered to perform various other tasks by simply choosing them from action menu, like "open door", "reload mag", "treat self" etc.
During a mission, a commander doesn't necessarily have the time to individually point at everything and since AI has already detected a mine, it knows where it is and it should be possible to order disarming that mine. {F19070}