Another impressive thing about the 17 reps is the balance and control required, having that added weight so far from the center of his grip on the DB's. That all requires extra strength.
He's pressing within his stronger ROM, somewhat reducing the potential of injury. Most guy's in gym's (now days) use that form, on the bar or with DB's. Semi-locking out (longer ROM) at the top, might invite injury even more so. Great lift by any standard.
