>> 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 doing the bare minimum of due diligence, they will have a bad time regardless of activation lock. I’ve seen people buy ancient MacBooks off eBay that can’t run the software they need, simply because they didn’t do the research. That isn’t the seller’s fault.

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.