Workout and exercise is an integral part of OMAD. Working out in a fasted state or before your eating window has an array of benefits which include an improved tostesterone level, brain health, and faster weight-loss among others.
I agree that you need to exercise when you are on a diet especially for weight loss because exercise complements the diet in reducing weight by burning calories. However, my concern in doing a workout while on OMAD is the weakened body. In my case, I feel weak when I am hungry so maybe the workout can be done after 2 weeks into OMAD when the body has already adjusted with the diet.