Like that saying, if it looks too good to be true...
A clean used car with < 10k miles on it, 99.9% of the time was badly damaged or stolen and messed up. A brand dealer would always, always, always retain a low mileage car in good to excellent condition. I would bet that the vast majority of these vehicles with the low miles, if well inspected, would show that they've had a fire, crash or vandalism and been repaired. Not a bad thing if they did a good job. Hint: most of these refurbers dont do a good job, just good enough to make it look good. I guess you'd have to ask yourself "Exactly how many people would buy a $50-60k car, drive it 3k or 8k miles, then trade it or sell it for $20k or $30k, with room for this dealer to add 2-3k for his profit and have it be a like-new vehicle?". Answer: Zero
The cars with higher mileage, particularly the ones noting "just came off lease" are a similar story. They came off lease alright, except the owner returned the car in awful condition. Think a bunch of dents, major carpet staining, dog jumping around on the seats for 3 years, changed the oil every 20,000 miles, used it as a four-wheel-drive except its a honda car, etc. You get the idea. The dealership who leased the car will then invoke the fine print clauses half the car leasers dont read and charge him a bazillion dollars in reconditioning fees. They then put that money in their pocket and drop the car on a wholesale refurbisher (like this company might be...if someone knows them and they're just the sales conduit, well...). The refurber fixes it up (bondo, some new carpet and seats, a few oil changes with some fastflush in them and a big can of gunk to keep the valves from rattling until after YOU change the oil, spray some tarry undercoating over the scraped undercarriage parts, etc).
Of course, nothing is assured when buying a used car. You're still better off buying one private sale, at least the average joe doesnt know how to fool a competent mechanic/appraiser. For a few hundred or thousand dollars, a pro can make a piece of crap you wouldnt sit in, let alone drive, look like a brand new car. Until you change the oil. Or that first really warm day comes up and you start wondering "whats that smell?" or you take it to the dealer for a repair to a warranty item and he says "sorry charlie, this car has been smashed up and the transmission problem you're having is a result of that...".
Didnt want to rain on the parade, just wanted people to keep their heads up.