Could it be that the ones with the "(EU)" tags are for the European version of the game, the ones with the "(US)" tags for the North American version, and the tag-less ones for the Japanese version?
Also, something tells me that the list isn't completely official (or the track list either).
Edit: Did another little scan of the beginning of the list and noticed that there is another premium car that they made for the game, but still included pretty much the same car that is standard which they imported from GT4. I already gave the BMW M5 example above (there is a premium 2008 model and a standard 2005 model, both the same car) and now I noticed that there is a standard 2003 Aston Martin DB9 and a premium 2006 DB9.
Does anyone else strike that as odd? Why the hell would there be a standard and premium version of virtually the same car? I just don't think PD would do something like that and I'm getting more and more convinced that that list needs some work and was probably released in a hurry.
Edit 2: I also believe there will be car packs released as DLC because I noticed quite a few cars that are in every other game and are quite popular that aren't on that list (e.g B7 Audi RS4 and Aston Martin V8 Vantage (not the 90's one, because that's on the list)).