Hi Crab! Long time no speak...
What an interesting thread! M Vuichard, FWIW, is an examiner with the Swiss CAA, with a long history of long lining and mountain flying. Not directly defending his technique - I have insufficient data for that. However, I do think it is one of the more interesting concepts that I have seen in my limited flying career (1983 - 2011).
Like others on here, I have always had a healthy respect for VRS, and used to teach my students to listen for/feel the aircraft growling at you as a warning - as they all will on a poorly flown, low-speed, and steep approach.
I also recall seeing an explanation of the origins of the terms VRS and SWP, but cannot now locate it. IIRC it has the US Army calling it one thing, and the USN the other - and no agreement on a common way forward. Imagine! (Quickstop v fast stop springs readily to mind).
All I will say on Vuichard is to keep an open mind. Until we see quality data from an unimpeachable (and not-for-profit) source, shall we consider that he might - just might - be on to something?