What it trains
Maximal and near-maximal strength through the phosphocreatine system: short efforts, long rests, low total volume relative to how hard each set feels. The adaptation is neural first and structural second — for the first six to eight weeks you are largely getting better at recruiting the muscle you already have, and only after that does cross-sectional area start moving.
Primary work covers the posterior chain (glutes, hamstrings, spinal erectors) through the hinge, the quadriceps and adductors through the squat, and the shoulder girdle and triceps through the press. Grip, bracing and trunk stiffness are trained implicitly on every lift rather than bolted on at the end.