There's no doubt that mixing these two could be a nightmare. But if you're replacing the pre-purchase haggling of a car dealership with the no-haggle process of buying on Amazon, then it might not be awful.

The real question is: who's on the hook if things aren't as described/pictured? It sounds like these all come with extended warranties, so that would mean it would be the dealer. They're no picnic to deal with, but that's going to be the case no matter whether you buy the car from them or from Amazon. If you can have a more pleasant buying experience by starting with Amazon, that's a win in my book.

As a knock-on effect, it could help bring down prices on used cars sold by other dealers, since buyers could point to these car listings as comparables.