I think it's entirely possible that his shooting has improved this year BECAUSE of his ankles last year. He was already a phenomenal shooter during his career. But given what we know now about his adjustment to playing on bad ankles, I'm certain that he learned a lot about his shooting mechanics and how to improve them to adjust last year. Now this year he's benefiting from that experience.
It reminds me of when I was in high school and I tore up the tendons/ligaments in one of my fingers on my shooting hand pretty bad during a game. I had to sit for like 4-6 weeks to let it heal. In the meantime, since I still had to attend practice, I would practice shooting with my left hand on one of the side hoops while the team was scrimmaging or whatever. Not only did I become a pretty decent left handed shooter, but all that work focusing on the shooting mechanics with my left hand reinforced good shooting mechanics with my right hand when my finger healed. To this day, when I sense that my shooting mechanics are sloppy (I only play like once a week anymore), I practice shooting with my left hand for a few minutes to force me to think about proper mechanics. It always helps.