Controversial ? Yes - that's what I was saying. If you are going to include a 75mm lens as a portrait and exclude a 135mm as a "classic portrait lens" that would certainly be a controversial viewpoint. The 3 most common portrait focal lengths (the "classics") are the high speed 85mm (often a 90mm on Rangefinders, sometimes - though far less often - an 80mm or a 90mm on an SLR), 105 and 135 lenses (Nikon's Defocus Control Lenses are available as a 105mm or a 135mm).
I don't know why we are bringing up 135mm lenses being hard to focus (or "couple" ) on a rangefinder when - to the best of my knowledge - none of the Sony Nex series or the Ricoh GXR are rangefinders, so it is an entirely irrelevant point . Your belief that a 90mm is not a portrait lens when it is on a crop camera is what we are discussing.
Maybe you are saying few people use 135mm lenses on a rangefinder due to this difficulty and that this somehow proves it is an inappropriate focal length for portraiture ? In which case, the SLR world say "Hello" to you.
I'm not sure if you even read the quote by Leica that you posted, but what they are saying is that on a Leica M8 (1.3x crop factor), the 75mm lens becomes equivalent to (replaces) the 90mm focal length which is often used as a portrait lens. This has not been in dispute by either of us ... 90mm is an appropriate focal length for portraiture (along with the other "classic portrait focal lengths" of 75mm,85mm,105mm and 135mm). This is simple history, though it may be of greater familiarity to somebody who knows something of SLR's rather than just Rangefinders.
At least you now acknowledge that ANY lens can be used as portraiture, which is radically different from your prior (erroneous assertion) that a 135mm equivalent is "well beyond a portrait FOV" ...
... which is simply what I corrected you on. So, it appears we are now in agreement.
PS - Leica has their Apo 135mm lens, so that would be the latest "Leica 135mm portrait lens" - not that that is of any relevance to this discussion, but you asked the question, so ...