Perhaps so, but it's a belief that has a foundation.
It's been stated before that the Daedric Princes created their own realms; they weren't "distributed". In addition, Duskweaver's link explains why that a "prince" is not necessarily an heir to a reigning monarch. A prince can be a ruler in his own right. Since the OP's argument is partly a semantic one, his argument is defeated by this.
The OP's other argument was that this hypothetical king would keep the Princes "in check". Since there's a lot of infighting and bad blood between the Principalities, that rules out that there's a supreme being "keeping the peace" between them or regulating their actions.
Besides, there is no precedent or evidence for the existence of a "Daedric king".