On that point, I see clearly wrong ads all the time. In fact, the guy that sold me these exact amps, his ad said they came with "Remote". He checked the "Remote Included" box on his ad when he listed it. Now, of course power amps don't have remotes. However, should I make him give me my money back because he did not ship the remotes?
Of course that's not really the same situation. Yes, the buyer is being more exacting than most of us would be, but there's no real value in speculating about why he's being difficult. You clearly want to do the right thing. If you can't get an original manual from the manufacturer (and you might ask them whether they come one per pair of monoblocks), then have him ship the stuff back to you and refund him all of the money when you have them. I'd make it very clear, though, that if there's a fingerprint on them, you'll send them right back to him. (And I'd arrange to check them out before officially taking delivery.)