IANAL, so I'm hoping I'm understanding this right: because Okrand wrote the dictionary, and in it claimed that he learned it from an actual Klingon, he may not now say he invented it? The argument kinda being, if the language is real, and he wrote a non-fiction authoratative book on it... then he can't be inconsistent about the origins?

It's hard for me to wrap my head around it, but it's hilariously clever if I'm reading it right.