When you have a clean medical amputation at that level there is not much risk to playing outside of popping the stitches and then having to wait a long time for healing to occur.
He probably was given a shot to numb the finger before the game and this would have had no impact on his performance as an OL.
In the long run, my guess is that doctor's thought the bone and soft tissue injury was so severe that chance of having a functional finger in the long run was poor. The main disadvantage he will notice in life is that his right hand power will be significantly diminished. For most fine motor tasks, there will be no problem.