Suffice it to say that I would be very skeptical of anyone who claimed that more +1s led to a higher search ranking in Google's web results.
(They fail to follow through with posts on G+ are naturally likely to get more +1s than likes, thus presumably debunking the whole correlation issue like you say. But anyway)
So my takeaway (which I am not sure if you are challenging) is that posts on plus.google did better than a presumably control sample on facebook - and the article incorrectly ascribes this to +1s. You seem to be saying, yes it did do better but its not because of +1s, its just better. But is it better content or is it better SEO-ness of the page.
Thats the part I would like to see these studies show - how they manage the control portion. How they control for quality of the content? Because if posting the same content on G+ and on a.n.other site gets you significantly more pagerank, then its really hard to argue not to do that.
(I quite accept the "its not +1's goddammit" argument)
I don't think he answered it. He basically avoided the question as expected. Not that I have anything against Cutts. There are probably things he can and cannot say or maybe he doesn't know.
That being said, he probably answered the question as well as he can or wants to. It's pointless to nitpick.
We can paraphrase that to: "Yes. I am saying that +1s make no difference in Google rankings."
The wonderful thing about the English language is that there are often many ways of saying the same thing.