Its a very logical requirement. Activating hero flash at 10th turn lets you summon a normal hero from your deck. It would be nice if there still were normal hero monsters in your deck at that moment. Very easy requirement to meet.
What could be worse than 4 normal heroes with different names? There is only 5 of them and 2 of them are level 3. Neos is not level 4 but it's still usable with Neos Fusion.
By the time of your 10th turn, you probably are going to have all normal Hero monsters in your hand...if the duel isn't already over. I don't mind the restrictions, but hope they at least lower the 4 Normal hero monsters requirement to 3.