I just want to point out that the HV chart is not designed for approach and landing (your shaded area would look very different). 50kt at 3-5 feet is ok for runway landing, but I would not like to be doing 50kt that close to the ground while landing on helipad. I have been taught the same way as you on my ppl course in EU and spent quite lot of energy to re-learn it during my further training in the states. Now I definitelly prefere constant angle approach with as smooth power changes as possible with loaded disc towards the end of approach.
Well these are actually two different szenarios:
The "H-V takeoff and landing" is definitely meant to be used as guidance for any runway takeoffs and landings. I've personally seen some big helo in Starvanger do exactly that H-V compilant takeof on Starvanger airport. Entering the hashed section of the H-V means that the pilot deliberately operates under circumstance "where a safe autorotation has NOT been demonstrated by the manufacturer", definitely a no-no for commercial runway ops.
The environment you are referring to is what my FTO called "approach to elevated helipad".
(we'd use a section of meadow raised 3 ft above the surrounding, app. 5 yards in diameter)
In this case all of them FIs insist that one travels along a straight line to the helipad, all H-V stuff is irrelevant, as one is meant to NOT need any excessive pitch or flare. The perfect approach is completed a good 30 ft before touchdown point, with regard to control input. They claim that would be the only safe way to approch a mountain landing zone, which typically is not providing any ground effect, and always running the risk of SWP.
The H-V compliant runway type is bullet proof as you always can enter flare and/or autorotation,
the mountain-LZ / elevated heliapd approach is inherently dangerous as you HAVE to be
in H-V constallations from where you cann't safely autorotate.
Of course we almost exclusively practize the helipad approach, as it requires much more precise planning and power control.