It’s not ideal but for a normal non tech savvy or no bitcoin person I could see how they wouldn’t understand the risk. For people who have been around for a while though it’s top tier retardation

Second-hand hardware is less about the seller knowing your seed than about a device that arrives pre-seeded. Factory reset, verify the firmware signature against the vendor's published one, then generate the wallet from your own dice rolls before a single sat goes to it. A seller who hands over a filled recovery card has already answered the question for you.