That's the reason why there is no emperor ingame. But the claim was there and if one king would have been powerful enough to rule whole Iberia it would be possible his claim would have been accepted. So the Empire makes sense.
It's one of the few de jure empires I actually don't mind much that it was added but I still think a custom empire makes a bit more sense. Even if you had the land you'd still need all sorts of prestige for your claim to be took seriously.
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