Does time play any role in this?

Can somebody burn the same amount of calories per hour in a short (< 2 hours) as in a long (> 4 hours) high-level performance ride? Or, in other words, can somebody maintain the same high-level performance (say, push 400 W, burn roughly 1 500 calories, per hour) in a short or long ride, if nutrition was not the issue?

Unless somebody looks like Vingegaard or other pros, who are at around 5% body-fat, is it necessary to match the calorie deficit entirely with sugar to achieve high-level performance?