So, I honestly don't know, it's a very small thing to focus on in the larger narrative of Napoleon's life but it is well known that Napoleon was suffering from digestive issues during the battle that may have forced him to be less active. However, it is well known that he died of Stomach cancer, something his father suffered from as well. With a host of bad stomach problems throughout his late life, it was hard for the Emperor to be active in the battle. However, as stated, I cannot verify it nor have I heard about it in commonly spread myths of the battle.