The rule was carried over from another tournament because the replay feature is only available in Heroes of Might and Magic V. Also, not everything can be seen in a replay (for example, mana is not deducted from heroes), and even if a hero levels up and gains a bonus to their stats, the replay won't show it. And this should be taken into account when compiling the final results table. Although, I don't deny that watching a replay can help you replay a battle. In general, the rule was more of an inheritance than a real necessity, as in previous installments.