I think there’s more to it though. It’s not just about having an insult help in interactions with all or even some NPCs. It really has to do with the predetermined nature of such an insult I think. That’s why this notion of NPC as puzzle comes up so much - it’s such a key point to understand the criticism.
Are you saying that "don't insult the Mad Tyrant" is "NPC as puzzle?" Leaving out whether and how much foreshadowing and all-a-that; some GMs will do better at conveying those things than others, and some games have specific mechanics for the PCs to find out things about the NPCs while interacting with them (IIRC there's something in 5E, but I'm AFB at the moment).