I think it was a little confusing/counter intuitive with what he was saying or how he said it. I don't have a problem with it, and he isn't wrong.
You do need to stagger some or end up in stagger to block the energy of the rear side into the front side to create rotation.
I think the problem most people have with too much stagger is like what HUB is saying, they aren't getting balanced on the front leg. It's also a symptom of trying to be like Simon or doing something without understanding it. They are shifting the whole body/head in the wrong way over to the stagger/humping the goat with the rear leg and collapsing into/behind the front leg. If you watch Simon, his head starts way over to the left in the x-step and he strides his front foot over so it's straight underneath his head/shoulders.
My upper body weighs too much to do that, gravity will pull me over before I can get my foot underneath me. Pretty sure that's why GG is so vertical in the x-step and then tilts going into the plant and lands in only slight stagger. Skinny people may have an easier time tilting over so much in the x-step, but I still don't think it's the most efficient way to move, look at the Jarvis brothers standing straight up in x-step.