That is true, some dimmers are very sensitive while others are not. If the temperature in the room where the enclosure is located changes frequently, the dimmer requires constant adjustment, but if the temps are fairly constant, dimmers can work pretty well.
My biggest issue with using a dimmer is the unreliable nature of them, so I can't go anywhere over-night with one hooked up incase the temps go up while I'm gone. That is why I gave up on them and bought a Ranco.