His stats give us the details for the games he has played so far. If people in this thread are going to insist (without any evidence) that what he has shown so far makes him a great passer and the next Carrick (which a lot of people are) then it's perfectly reasonable to show actual information that shows they are wrong.
I see your point and I agree that using stat brings good information to the discussion.
But when you use statistics it is (often) useful to put it into a context. The context you put it into, comparing his numbers to Man Utd-players, dont make much sense in my opinion. I’m certain that both Herrera, Matic and Pogbas completion rate would be a lot worse in NUFC.
Furthermore, you use the numbers as proof that his passing is not good. Fact is, his completion rate is 8 % better than the average of his team mates. I would argue that, isolated, sounds good. Considering the teams he has faced in the few matches he played, it is probably even better. Add that he is a rookie in the PL with limited game time, I might even put it as impressive and a sign that his passing ability is a strength and an area that has real potential (which is probably what people see in the way he passes; potential).
And now I just looked at completion rate. The same rationale will apply to key passes etc.
In my opinion, the numbers dont show that people are wrong. Probably not that they are correct either, because it is based on limited game time.