The video quality isn't all that good, but I think I see the elevator deflected up to attain the nose-high attitude. This would point to high load and/or density altitude rather than (only) aft cg.
At an extremely aft cg, the aircraft would still perform well, but the pilot would run out of elevator authority to stop the nose from coming up. You'd expect more something like a steep climb until a wing drops and the aircraft coming down in an incipient spin.
Erik.