chances are that he has done this already for a long time. I would wonder about the possibility of repetitive stress injuries. With that many reps and sets per exercise, he probably only does a few, and does them every time he works out (pure conjecture).
As Natalie says, low weight and high reps are the hallmark of work on muscular endurance but I would not use that many reps and sets even for that.
It certainly is different from the general recommendation of using higher weight and fewer reps to build strength, and I would try to encourage the client to change. I would expect reluctance on his part, though. Maybe you can make some publications available to him like this one from the NIH which suggests a different way of training. http://nihseniorhealth.gov/exerciseandphysicalactivityexercisestotry/str…