I suppose it comes down to whether they *know* that it's something they need to research. What do you mean, fanon isn't accurate?

(Or, hell, ignore the muggle rules of how nobility works, and engage in world-building! I would happily follow along with that! ...now I kinda want to write something where Harry finds out he's a lord, and goes to find Hermione, and they both engage in a bit of screaming about how the magical world handles nobility.)