Kudos to Ka -2b Pilot for raising the question that should first come to mind.
Highly localized downdrafts are far from an unknown phenomenon at coastal boundaries, as he says and can be accentuated by topographic features. There were at least two hills in the immediate vicinity of 200ft. With the tolerances required for the manoeuvre even localized 20/ft sec winds would erase the margin of safety implied by the visuals in 20 secs, i.e. the manoeuvre gets squashed to the ground.
Yet there is little discussion along this obvious first line of inquiry.