Well, it's from the PHB section on defining alignment.
Lawful Neutral, "Judge": Ember, a monk who follows her discipline without being swayed either by the demands of those in need or by the temptations of evil, is lawful neutral.So, both are unswayed by moral debate, so that's the same. And both are devoted to getting better at a skill, so that's the same. So why does this establish why Ember is Lawful and Mialee is Not-Lawful? I have no idea.Neutral, "Undecided": Mialee, a wizard who devotes herself to her art and is bored by the semantics of moral debate, is neutral.
That's the tip of the iceberg though. For example, we're given all these adjectives which supposedly describe Law and Chaos, and few of them actually contradict each other. You can be honorable and love freedom. You can be adaptable and trustworthy. You can be closed-minded and reckless. You can resent authority and be obedient to authority. These things are neither opposed nor even usually found in different people. Closed-mindedness tends to beget recklessness. Obedience often breeds resentment. Respecting freedom is honorable. Being adaptable makes you more worthy of trust.
And then there's stuff like Good and Evil. A Lawful Good character is described as acting as a person is expected or required to act, but fighting their enemies without mercy. A Lawful Evil person is described as playing by the rules, but without mercy.
And then we get things like the Book of Exalted Deeds, or quotes from Gygax himself about how Lawful Good people should slaughter women and children of the losing side because they might grow up to be Evil, and execute prisoners who convert to Lawful Good so that they can go onto their reward before they backslide.