Instead of doing 6 sets on bench in one workout, those sets are spread over the course of a week (2 on Mon, 2 on Wed, 2 on Fri). Either way the muscle sees 6 sets each week, however, with HST the distribution of the loading sessions creates a consistent environment conducive to hypertrophy. When you do all six sets at once, you put unnecessary drain on the central nervous system (CNS) and invite centralized overtraining symptoms and burnout.
It seems like an incredible amount of brosciencey bullshit and assumes that you have AIDS wasting disease. Other than that, you can't really fault it. I'm not exactly sure what it means by "hypertrophy specific" though. Training specifically for hypertrophy? I can't even explicate how stupid that is