It's how the ebay & paypal world has transformed everything so you are protected both as a buyer and a seller for these types of purchases.
The powerboat scene is full of all sorts. One boat I bought - the seller clearly knew about the damaged big end on one of the motors when I bought it.
Another chap - well known when he does work on a motor for switching out your good bits (wiring looms, alternators etc) with knackered bits. But if you call him out on it, he'll want a fight accusing you of calling him a liar. Little does he know people have UV marked their stuff before putting it in to him. But he doesn't care.