sorry to go off topic before as well
but I do believe the the times are valid, the manufacturers use only a handful of drivers all of whom have done thousands of hours on the track and know it as well as the back of their hand if not better.
An example is that Nissan use the one driver "Dirk Schoymans (sp)" (which is one of the drivers that both Porsche and Ferrari use), for all their testing of the GTR's.
The good thing about Nurburgring and the reason why car manufacturers and tyre manufacturers test on it is that it has so many varying conditions over the track length which make any short comings of the car really show themselves and not be hidden by some clever "this track only" setups.
In my opinion (not that that means much lol) it shows the true performance of the car in everyday road going situations and is a far better indicator than say a short track.
I also think I read somewhere that the true lap record runs are done on a closed track, not on the tourist drive around days.