Frozen and loaded up, the mat side isn't just a snack - it's a sustained, repetitive activity, and that repetition is the point. Research on licking behaviour consistently points to the same mechanism: the repetitive motion triggers endorphin release and activates the parasympathetic nervous system - the 'rest and digest' state, the same system a good walk helps switch on. Heart rate comes down, focus narrows to one task, and the nervous energy that would otherwise go into pacing, whining, or door-watching gets somewhere to go instead.
It's not a substitute for physical exercise - a walk and a lick session do different jobs. But on a rainy day, before you leave the house, during a thunderstorm, or right before a nail trim, a 15-20 minute session on the mat gives your dog the same kind of settled, worked-through-it calm that a walk gives them, without needing a lead or good weather.