What it trains
Usable range rather than passive flexibility — the difference being whether you can produce force in a position, not merely arrive at it. Work is largely isometric and slow eccentric, holding end-range positions under light load so the nervous system stops guarding them.
The ranges prioritised are the ones a desk-based week costs you: hip extension and internal rotation, thoracic extension and rotation, ankle dorsiflexion, and overhead shoulder position. Those four also happen to be the four that most often limit a squat, a press and a deadlift, which is why this class sits on the timetable next to them rather than as an afterthought at the end of the week.