My guess its not about revenge but being able to talk to him in person a few times a year.
In all seriousness, I think it is TJ taking the high road because it's best for Iowa State.
Badmouthing former players would be a bad look for a coach who recruits based on relationships and having the genuine best interest of his players at heart. Disparaging Hunter could hurt TJ and the program, saying nice things about him (such as hoping he lands in the best conference) could only help.