I’m not sure because it seems like we have very different ideas of what “completeness” means. I do think being incomplete, as I understand it, is a bad thing for an RPG because it would make the game unplayable in certain circumstances.
Any consistent formal game (D&D) within which a certain amount of elementary gameplay can be carried out is incomplete; i.e., there are statements of the language of D&D which can neither be proved nor disproved.
The Rules Lawyer's Incompleteness Theorem