Right, but I think that the point that is being made is that the prosecution was claiming in 2009 that the clock was 10 minutes fast (so they could prove their lie about calling 112 after the police arrived), and therefore they could not use an 8:53 video of "Amanda" at the garage, because she would have been talking to Popovic at that time (i.e., 8:43 if the clock is fast as claimed by the prosecution).
So, weighing the damage that would be done by the 112 Call issue, against the possibility of anyone identifying the video to Amanda Knox, they went with the "clock fast" story and disregarded the video.
Now we know the video is really from 9:03. In fact, the person in the video might be the second-to-last person to have seen Kercher alive. Too bad the police didn't investigate the lead, but I suppose it would have rubbished their silly 112 argument/lie if they had actually done their job, investigated, and found the person. So, they didn't.