"Don't spare yourself" seems to be the key motivating factor in this Zen monastery. By working hard and not wasting a moment even in lying down they are training their subconscious to become infected with the enthusiasm. If they keep at this until it becomes a habit, soon the rest of their being obeys. Until then they need the keisaku (stick) wielding Jikijitsu.
Theravada retreats can set a gruelling pace too - the make you wake up at dawn and meditate all day on one meal a day. The teacher can get quite worked up if a student misses a sitting. Of course, some Zendos like here can take it to the extreme.
This harsh self denial isn't exclusively Zen or Buddhist, here's Sadhguru Jaggi Vasudev, the Hindu mystic warning against mollycoddling the self in times of illness (Youtube video).
Armies do this too; in boot camps new recruits wake up at the crack of dawn, and make the bed neatly in precise moves, and completed in 20 seconds. Next, a morning shower in exactly 2 minutes and so on. Initially they of course only act like they are self disciplined to avoid punishment, but soon acting sharp and smart becomes a life long habit even without the drill sergeant.
Thich Nhat Hanh, the Vietnamese Zen master disagrees with the use of the keisaku and likes to joke that no one here beats people with a stick unlike in other Zen monasteries. Motivation and encouragement is given through love to oneself and one's inner subconscious. As the other answerer noted, Plum Village has an air of deliberate compassion. There's no hurry, but there's no laziness either. In my opinion, we could all use more places like Plum Village, but it is my experience that PV's gentle way is the exception not the rule. I haven't practiced with Ajahn Brahm, but from his talks he hints that he is very gentle with his students, unlike other Theravada retreats.