Lol really?
That's rather annoying. They should understand that people can use both and both can work well to maintain heat.
It really doesn't matter if you use just the UTH or both the UTH+bulb as long as you can achieve the proper temps.
However, if you are able achieve those temps with just the UTH, then I always encourage sticking to that only. I find that adding the bulbs just adds unnecessary work to maintain humidity.