Correct. Pick one behavior to click during a session. It’s up to you if you are looking for a down at the truffle or the paw at the truffle. If he moves the target when he alerts, it’s not a big deal. Reward at the source. You can hold it down once you arrive if he continues to push it around. The key is that he is showing the truffle to you, not you showing the truffle to him.
Boxes moving around isn’t anything to worry about. Truffles don’t grow in boxes and they won’t be as easily dislodged from the ground. In the long run, Salu will be expected to locate a dislodged truffle in the field so this simply sets a foundation for the long term.