Whether or not a second UTH is needed depends entirely on the ambient temps of the room that the enclosure is kept in. If the room's ambient temps are steady and consistently around 80*, and he has a small uth to create a basking spot....that sounds fine.

If the room is chilly (or suffers from wide swings in temps) then a second, larger uth is a good idea...properly controlled with its own thermostat, of course.