I mentioned in posts No's 7 & 9 that it appears to be an approach to a precautionary landing at a suitable open space. This would indicate (as I mentioned) an existing fault indication and the freewhel fits this scenario, whereas a drive shaft failure is very unlikely to have given any prior indication.
Again putting on my Monday morning umpire's hat, I would have set up a far steeper approach to allow for the possibility of it turning into an auto with only the landing area as a suitable destination. It happened to me once (compressor failure on short finals to a floating pontoon) and I make the point long and loud to anyone who will listen: a steep approach is the only guard against losing power on short final that will assure a landing at the planned site for a single engine helicopter.
Rotor flicker/speed on a smartphone video is totally unreliable. Search for videos of stationary blades in flight, what you see on the video is unlikely to have any similarity to what actually happened.