Some people find that any exercise, even HIIT reduces their BG levels, while for others only gently exercise will have that effect and like you more vigorous exercise will raise them (liver helping out).
Similarly some find that fasting for longer will reduce their BG at the end of the fast, but for others it will slowly keep rising until they eat.
I found that my particular DP (Dawn Phenomenon) meant that my BG would start out quite high for some ( at around 7.8) and then often rise a little until I either had some food or exercise. After a breakfast of boiled eggs or cheese (or other zero carb meal) it would fall . Similarly with gentle exercise.
We are all different, in both our reactions to carbs and the way our livers and pancreas' help us out.