This assumes the carabinieri drove right by the cottage they were looking for, on the wrong side of the road, angled into its driveway as if parking, and failed to notice the small crowd gathered standing around outside that had summoned them, and that the male figure that walks in front of the camera with a distinctive bold stripe running vertically down his pants, similar to the carabinieri uniform which features a distinctive bold stripe running vertically down their pants, is not in fact a carabinieri officer.
So for me the timing of the CCTV is easy. The postal police say they arrived at 12:35 and that is consistent with them struggling to find the address and ringing Knox using Filomena's phone at 12:34. She tells them she will come down to the street and wave. So there is no discrepancy in the CCTV.
Now I realize that is reasoning you can't use or accept, so I will try and point out the mistakes in the defense case.
The first problem here
http://www.amandaknoxcase.com/defense-cctv-presentation/
is that the defense has incorrectly marked the camera angle on the satellite photo. From this they incorrectly conclude the police car of 13:22:37.99 has turned into the driveway. In fact it has stopped on a small layby that is visible in the satellite photo just past the driveway. We know it has stopped because it hasn't moved from the previous image found on this site and ignored by the defense
http://themurderofmeredithkercher.com/PDF/Postale/postale 124.jpg
So the car is stationary.
Because 7 via della Pergola isn't actually on via della Pergola, rather it is on viale Sant Antonio, it is legitimately hard to find. What has happened is that on the first lap, the police car has turned out of via della Pergola, stopped on the side of the road and said: "where the hell is it"
The image you believe is a policeman that walks past a full 33 seconds before the police car arrives, cannot be identified with any certainty as a policeman. You may see a stripe on the trousers in the CCTV image, in my view the resolution is far too bad to pick up such detail. There doesn't seem any link between that man and the car that parks 33 seconds later.
Other problems with the defense presentation is they ignore the fact that Alteri and Zaroli also turn up and they attribute legs that could easily belong to them, to the postal police.
There is no visible small crowd awaiting the police car in any CCTV images.
So in sum, I think Nencini got it right. At best you could say that there is some doubt, but mostly it is due to a poor reconstruction by the defense that confused a layby with a driveway and then suppressed some images that showed the police car was stationary.