That he was essentially able to regain his feet with continuous momentum without use of his hands, (he was effectively leveraging against the French player even though his right hand did touch the ground) I think it is relatively straight forward is easy to argue that the tackle was not completed and he had the right to continue.
It's like asking the correct question around a questionable try, and depending on the phrasing of the question you might ask yourself, you might come up with differing and contradictory answers.
Was he tackled? - in the laws
Was the tackle completed? - not in the laws but relevant to every tackle situation
