I get DP, and the longer I go without eating, and the more exercise I do, the higher my blood glucose rises - right up to the point where my blood glucose level drops sharply, and I feel a bit wobbly.
Basically, it is horses for courses. Some people do better with brekkie, and others don't.
I would recommend that everyone actually checks their blood glucose across several mornings before they make any decisions on whether to eat, or exercise, or not.
Test on waking. If your bg has risen overnight, that is a good sign of DP
then test once you are up and about, if your bg rises with early morning activity, that is sometimes known as 'foot on floor phenomenon'

Then test after breakfast (protein and fat breakfasts or snacks usually make
my bg drop in the mornings, showing that they are countering the phenomenon, other ppl report that a few grams of carbs suit them better)
Then do the same test to see what fasting does, with or without exercise.
In my case, I wake up in the 6s, and will rise faster the more active I am. It usually goes up to 7+ with the simple action of showering and going downstairs. At that point I eat or drink something (it can be as small as a Babybel, or a couple of mouthfuls of a hot drink with cream in it). That seems to signal to my liver that it doesn't need to keep pumping out glucose, and things settle back down to the 6s within a very few minutes, and then will slowly drift downwards until I eat a proper meal, often a late lunch at 2pm.
On the other hand, if I didn't have that tiny snack, and decided to exercise, I could easily hit the 10s before it drops.
I believe, but have no way of testing this, that my DP is due to having wackier hormone dysfunction than most people, and the Libre has shown me that it is more Foot On Floor than Dawn Phenomenon. But unless we each do the necessary testing ourselves, to work out the difference, it is usually referred to as DP. There are several different hormones that work together to create Dawn Phenomenon, and insulin and insulin resistance are just two factors.
Oh, and I am never hungry for breakfast, but eating it will often give me better blood glucose control (and more hunger) through the day. Whereas others report differently.