I am pretty suspicious about this story, and I don't like it. It's not a good example and it does not clearly demonstrate 'skillful means', the defining quality of Zen aimed at bringing students to direct insight with unconventional methods. It seems more like an excuse for bullying.
Maybe there is more to the story, a transgression by the student, or a turning away from their 'wall' of lack of realisation for the distraction of 'pearls of wisdom' justifying an extreme method, but to me it sounds like bad Zen, a misconstrual or minterpretation of the method. The implication to a student of the story is only, stop following.
One of the most controversial Zen stories about the posing of a koan, for the Zen community, is the story of Nansen and the cat. One of the five precepts taken to become a Buddhist is to abstain from violence. And the Buddha said in the parable of the saw "Monks, even if bandits were to savagely sever you, limb by limb, with a double-handled saw, even then, whoever of you harbors ill will at heart would not be upholding my Teaching." Nansen is said to have cut a cat in two with a sword. Good arguments have been made that the students were involved in a common argument for Buddhists, is it ethical to keep a cat that kills mice? Nansen goes directly to ending the interminable discussion. If you don't want the cat, do you want the mice? If you want the cat can you say a good word for it? Dogen, the great(est?) Japanese Zen master says Nansen did teach with this, but could have been more skillful, and gives an alternate way he would have taught without the cat dying. Similarly, breaking a students leg is not skilful, even if it 'works' and teaches the student a profound lesson. As last resort to avoid a wasted life not awakening, maybe. Does the story make it clear this is a last resort? No.
It is a common perspective in the West that Zen stories and koans are interchangeable, and that any student can learn by contemplating any of them. Which makes a muddle of the whole thing. So some context. Koans and koan practice come out of the 'Transmission Of The Lamp' genre of writing, descriptions of the moment a master was recognised (and elements of their biography), that record the 'direct transmission from mind to mind' which creates the Zen lineage. They are directed at people knowledgable of the Buddhist Tripitakas and Zen literature, and often feature encounters with other spiritual practices like Daoism, or sophisticated reaction to and refinement of Zen doctrines - like Caodong's question about how insentient beings can preach the dharma or Dogen's question why Buddha came from the West. Koan practice is not about turning away from questioning, or abandoning the idea of answers, but in contemplating the defining moments of realisation of great masters a deep challanve is being undertaken. It is directed toward "A special transmission outside the scriptures; No dependence on words and letters; Direct pointing to the mind of man; Seeing into one's nature and attaining Buddhahood." (attributed to Boddhidharma, 1st patriarch of Zen)
"For there is suffering, but none who suffers; Doing exists although there is no doer. Extinction is but no extinguished person; Although there is a path, there is no goer." - Visuddhimagga XVI 90. Not even a hobbling goer