The human body isn't so fragile that one can completely twist and snap a spine with bare hands in an instant, that sort of thing isn't as simple as just twisting lightly like in the movies.
Gao Yang had learned from Li Jinfang how to twist a neck, but this sort of thing is far from achievable with technique alone.
Li Jinfang had been practicing martial arts since he was young, his arm strength and explosive power were simply not something Gao Yang could match. After practicing with Jiang Yun for a few days and knowing how to apply force to the more vulnerable areas of the neck, Li Jinfang could twist a neck as easily as wringing a chicken's, but for Gao Yang, after a few days of learning, it would not be too late to think about twisting a neck only after training his upper body strength to a level closer to Li Jinfang's.