I find the 2-year-rule (or practise if there is no rule) really weird and a bit on a nonsense side to be perfectly honest.

Also I think there are two possible reasons he wants to keep it. Either he thinks contact is not good for you and not having it is the right thing to do professionally or he does not want to keep contact for his own reasons. I am not suggesting he doesn't like you or such, but the reasons might be something he doesn't want to share, ever and coming from the mindset he is in atm.

I am wondering if it would be best to try to stay in touch with people that does not have limitations of any kind: friends, co-workers, people in hobbies etc. And trust that time will tell if you and T are reconnecting at some point.