ACSM states that one set of 12-15 reps per major muscle group is efficient to meet most basic fitness goals. So my thoughts are that this much volume really isn’t imposing much demand for the body to really adapt, especially if the weight isn’t increased periodically. There is another question here too, is this much volume for single or multi-joint exercises? I would be concerned about overuse injuries for single joint exercises more than multi-joint. I believe this to be the case because of the synergistics of multi-joint movements, plus, I have a few half and full marathon runners who are in there late 60s and early 70s and never suffer from overuse injuries, and they run a lot of volume.
I agree with the comments from Martin, speed of movement could be a deciding factor on whether he is causing any demands to his energy systems. I would also be sure to approach the subject with the gentleman in a neutral way if you haven’t any rapport with him.