And yet, if a player told me that their warlock has no patron, and instead, in keeping wit the Fey lore I've established in the world and adding to it, has bound fey magic to their will by enacting ancient pacts in ancient places, drawing directly upon the power of The Glade of Twilight's Yearning, and the Bridge of Whispers, and the Halls of Obsidian Night, and is slowing becoming Fey as they use this power and grow in it, I would have clarifying questions and ideas to build on it, but I wouldn't consider it a normal thing to tell them they can't decide what their class mechanics mean in the fiction.