I like your reasoning here. There's another nuance too: disorders mean someone's life is out of order. Like Dr Ramini usually says, "we can't diagnose jerks". If someone's grandiosity or self-centeredness is not causing THEMSELVES any harm, that's not a disorder, they're just mean. The thing with NPD is people who suffer from it are usually "looking for" happiness, they're dissatisfied, they try to control external people and things bc they believe this control will bring them the happiness to get them out of that misery. But it's a misguided thought pattern. Hence, a disorder.