Sio did what he said. He made sure to make up for lost time by training his great-granddaughter. He also included Zach and Nessa in that training because they were Violina's friends and once he got started, he had trouble stopping.
He had so much knowledge, wisdom, and experience when it came to training and fighting that he just wanted to share with the younger generations. He also saw it as a personal challenge to get Zach to use his energy.
Zach and the others weren't sure if they could say that Sio was the best teacher. He was great. He knew a lot, and eh was strong. But it felt like he relied on brute-forcing their learning by just making them suffer, whether it be through nigh-torturous physical training or spars and mock-battles with him that were only one-sided beatings with a pseudonym.
It was effective, though.
He helped Violina with her sword techniques, physical strength, and the skill that covered her sword or whatever she touched in ice.