I just had this in Hawaii (Big Island). Dollar car rental dude checks my car when I return it and decided some scratch on the fender was new (I'm pretty sure it was not). I had full insurance and I told him he can figure it out with the insurance company, that I was in rush to catch my flight, and he can do whatever he wants. They didn't do anything. They're just looking for some sucker they can charge extra on some random thing.

I've had a lot of rental car experiences. Usually it's fine. Taking photos sounds like a good idea.