Please keep in mind that these were rules that you apply to a _toy_ project. You apply the rules once, blindly, even if they don't make sense to you at the mome

Please keep in mind that these were rules that you apply to a _toy_ project. You apply the rules once, blindly, even if they don't make sense to you at the moment. Then, when you work on a real thing, you may remember, for example, to create a dedicated PhoneNumber class with strict rules (e.g. E164) instead of a string that gets shuffled around with no one really knowing whats inside. Or you just forget the rules as a nonsense and move on. You seem to be criticizing the 'rules' as if they are suggested for production code. You couldn't be seriously thinking someone suggest maximum-of-2-fields as some sort guideline for the real world.