Lensrentals.com has reported what you say above, based on some serious measuring equipment. SO I can't argue the facts.
I do believe the old zoom had far more copy variation. I have shot with sharp copies and soft copies. We've seen very few (if any?) reports of the new zoom being a "soft copy"
Subjectively, I felt that the new zoom was the equal of the old prime, and really beat the old zoom.
I go back and look at the old zoom images I have, they were all stopped down a bit as i tend to shoot it , and it was very good.
The new lens is just better, and does not require as much stopping down (better wide open) and works very well with a 1.4x TC. The old version was bad with a TC.
The biggest advantages of the new vs. old are all described in the first post of this thread, that is AF speed and accuracy (keeper rate will go up) and much better IS.
Thank you for your response. That is what I was looking for.