You can have liver dumps at any time of the day or night. Dawn Phenomena is so called because it happens around that time, the liver dumps glucose into your bloodstream to give you the energy you need to start your day. As you have been fasting while you are sleeping for a good few hours your body needs this glucose. Liver dumps at other times will happen, for instance when you are awake but havn't eaten for a few hours.
The trouble with those of us with PreD or T2 is that until we gain better control our liver's splurge at greater levels.