There’s an entire thread correcting this assumption by none other than Rob Kuntz himself. And great news! It’s on the front page. So we don’t need to rehash the whole thing again here....
You are correct if Rob Kuntz is indeed correct which I would say he is not. Rob contributed to the Greyhawk OD&D supplement and bit to Deities & Demigods. So.his mechanical contribution is slightly more than Arneson.
Arneson had a great idea but his mechanical contribution to the early game is near zero. Anything else is blatant revisionism.