the Big Buddy sessions: it's the heads they're working on
The what looks like sadism, the skeletal stress, the fatigue. The suffering unites us. [...] it's not about the physical anymore, men. The physical stuff's just pro forma. It's the heads they're working on here, boys. Day and year in and out. A whole program.
Context
The exposition's hinge: the engineered suffering — "the skeletal stress, the fatigue" — is a bonding technology ("the suffering unites us"), and past a certain point the regimen stops being about the body at all. "It's not about the physical anymore… The physical stuff's just pro forma. It's the heads they're working on here." The academy's real curriculum is psychological conditioning delivered through the body; the drilling is the medium, the mind the target, "a whole program" running day and year in and out.