We've traded in a couple of vehicles at different ends of the age spectrum. They only relied on the photos submitted, which do cover all angles, but are really too far away to see much detail - at actual delivery time, they literally didn't look at either vehicle, just took the keys. Of course their valuations were undervalued by a few thousand, so that's probably what covers them.
The older one was a 17-year old Porsche, at that age they start to actually climbing back up in value slowly. Ours had no dents or scratches, but a major accident many years prior had replaced many of the body panels around the entire car. The bigger issues were it needed a new softtop (embedded plastic rear window was brittle and disintegrating), and probably a new catalytic converter (occasional engine codes related to emissions, though it would still pass actual tailpipe emissions tests) - if replaced with new parts, would have been more than the car value, though I suppose used dealers could fix it more cheaply..
Again they didn't even look at the car, and even if they did, what employee at the sales center or delivery center is qualified to assess and re-adjust the value anyways, no one...
