One of the drills they were doing was one-on-one, with the defender having no stick. That's very uncomfortable.
And, from a person who doesn't understand hockey, might seem odd or useless or dumb. But what it does is force you to move your feet and stay right on your man. It's a bad habit when defending to rely too much on your stick. Your stick is 100% useful in playing defense, and you can make plays with it, but your positioning and mobility are more effective. The puck is MUCH smaller than the man, therefore stop the bigger target. They played A TON of stick-checking hockey the last few seasons. It's a bad tact.
I think it's what he was mentioning when he said he was asking Terry why he got beat on a drill and Terry didn't really have an answer. It was probably something along the lines of him relying too much on his stickwork to play defense, and not utilizing his mobility and positioning.
There was a clip from rookie development camp where McIlvane was explaining to Carlsson about eliminating a play. He (paraphrased) said "Look, you have the size and the skating ability, you don't have to blow guys up to kill the play. Use your body and just get in their way, cut them off."