I see Retief as a swinger. Check this link on youtube:
(you can hit pause/play - pause/play to slow it down more)
To me - it appears he is pulling the club from the end, versus using his shoulder as a backstop and driving his right forearm. At :31 seconds is a great shot of longitudinal acceleration - shaft bent down, etc.
Check out this with Trevino:
Start around 19 seconds but watch (and pause/play) at 22 seconds (not sure who posted the vid, but they reference angled hinging):
To me, it looks like he uses his right shoulder as a backstop - then drives his shoulder/right forearm downplane and actually looks like his right forearm chases the ball.....in fact, he talks about turning in the barrel - and a closed clubface, etc. Great video - priceless.
Just my perspective.
Hinging, in itself, occurs during the impact interval - per 7-10.
I personally do not see Retief as right arm swinging - to me he looks like a manipulated swinger. Appears shoulder turn takeaway, blah blah blah.
As far as impact - I have still at my house. Yes, his post impact is funky - crazy really. But, having seen him 4 times in person, and video - he hits down. I mean bigtime down. Doesnt look like it in the video, but standing in front of him is a different perspective.
One last thought: His post impact flip seems to be caused by his left elbow bending outwards, towards the target - I would think there is a correlation there........