A lot of people are getting confused with the V5 statement of previous owners as it does not count the current one. But it is an easy trick for the dealer to uptalk by selectively using the information. It is the same for the service stamps. He found 8 services with Mazda and he is selling that.
It is amazing how he sells it for £2K+ of profit plus the finance and warranty commision. There was no way he could make such profit with cash buy. He is basically selling at approved used price to people who live near to him.
As you say, the car is rusty and when you part exchanged it, they could not sell it and it went down the auction route and now it is on sale for a profit.