Uber tight indeed. He must have thought that you won't call this river with anything less than Joker-3-xx and decided to check-call you down to protect his stack.

I once saw a guy cold call a solid bet on the river (when no one was left to act) when he had a royal flush on a $25 table. I can't remmeber if the board was paired. Afterwards he said, "I wanted to show it".