> But going by what a lot of people do, they will get a workout of thirty minutes burning maybe 200-300 calories, then reward themselves with a Big Mac at 550 calories,
The effect of exercise plus an additional Big Mac does not reinforce the claim that "exercise on its own doesn't lead to weight loss", because "plus a Big Mac" is not "on its own".
> and they probably already had a caloric intake in excess of maintenance (hence why they are exercising to lose weight, and more likely to go for that reward)
The reason why they are exercising to lose weight is probably that they have a current weight above their desired weight. That doesn't mean that they have a current calorie surplus -- plenty of people seek to lose weight when their current weight is stable but above their desired weight.
The effect of exercise plus an additional Big Mac does not reinforce the claim that "exercise on its own doesn't lead to weight loss", because "plus a Big Mac" is not "on its own".
> and they probably already had a caloric intake in excess of maintenance (hence why they are exercising to lose weight, and more likely to go for that reward)
The reason why they are exercising to lose weight is probably that they have a current weight above their desired weight. That doesn't mean that they have a current calorie surplus -- plenty of people seek to lose weight when their current weight is stable but above their desired weight.