Actually, he does. With IP contracts the onus falls on the buyer, not the seller, who is granted full ownership of their work from the moment of creation. Making sure you have clear title to the the work of another isn't the contractor's responsibility, it's yours.

That said, there are a ton of things having to do with the scope of work, reviews of work in progress, acceptance or rejection of completed work, and payment terms that are absolutly the contractor's responsibility. But again, securing clear title to the work is the buyer's concern, not the seller's.