I'd change that slightly, and say "AD&D 1e has very detailed tools to help determine NPC attitude, loyalty, and morale."
The 1e DMG provides a wealth of tools, tables, subsystems, lists, and such. Some might be considered rules, others might not. In the case of NPCs, note that the DMG has this to say: "It is often highly desirable, if not absolutely necessary, to have well-developed non-player characters (NPCs). In order to easily develop these personae, the tables below are offered for consideration…" In the case of NPC loyalty, the DMG notes "If you are certain of your DM ability, most of these factors [which affect loyalty and morale] should be apparent without actually checking them out, simply by empathizing with the character or group in question, and having them act accordingly."
Tool or rule? Depends, I suppose.