>> The buyer should make the seller aware of the problem, because it is in the buyer's interest not to end up with scrap.

How does this assume anything about the owner/seller?

It’s entirely on the buyer to make sure they’re getting what they want out of a transaction as long as the seller is not misrepresenting the product, and activation lock has been a thing for like a decade on Apple devices, so it should be widely known. If they make major purchases without even researching the bare minimum of what to look for, they will have a bad time regardless of activation lock. If the seller is misrepresenting the product as having the activation lock removed when it isn’t, that becomes a legal issue. On platforms like eBay, they will happily side with the buyer and refund them in cases like that. For B2B stuff, that’s why lawyers exist, but things can get messy.