Yes, the laser scanning can detect small differences, but they don't check all of the surface of the track - You've seen the pictures. Close the camera car they probably scan every 30cm, further away once a meter. Then they move up and do it again, so it overlaps a bit, and then they do the fiddly bits. But what if they don't pick up on an important fiddly bit? It'll just be forgotten, but that could be the critical thing that makes the corner what it is.
As for tyre models, I disagree. Regardless of the tyre model, in an ideal world we'd still prefer to race on a real track that was real - hell, that might even highlight flaws in the tyre model that could be improved that we don't see with a less accurate track.
And I'm well aware that making a 10GB track file and expecting us to buy super computers from Sauber to play it is too much (at the moment). There has to be compromise. I just hope that the important details are found, used and retained, even if that means reducing the complexity of the grandstand modelling.
By the way, when you're hitting bumps at 150mph, a bump that is 2mm too high goes from being perhaps unnoticeable to being a critical factor in how the track is driven. 2mm accuracy - for those that think laser scanning results in a realistic track from a driving point of view - isn't enough. Least of all when the points taken are so far apart.
The laser scanning ensures the track is close to reality, but doesn't mean that it's an accurate recreation of the track surface.