He Probably doesn't want to open a claim because he may have a record of doing these swap-and-threaten tactics in the past. Ebay flags accounts for further investigation for too many claims opened especially on high risk items.
I would say unless he opens a claim, don't bother with it. And if you have detailed pictures in the auction including the serial number and does not match what he received then they may find in your favor.
important note *all* communications should stay in ebay. That way if they say anything out of the ordinary it'll be enough rope for them to hang themselves with.
Film (Working RF): Canon 7, Fed-2A, Argus C3, Mercury II
Digital: Olympus E-M5, E-P3