I have never experienced any problem in this regard with any of the cameras or lenses I use.
I use a variety of Manfrotto tripods, all of which have one or other of the RC2 heads attached.
On each of my camera bodies (Nikon D800 and D800E currently, but have used D80, D300 and D3s in the past) and on each of my long lenses (up to 600mm), I have an RC2 quick release plate firmly screwed in place on a semi-permanent basis. This set-up gives a completely firm and stable basis for attaching the camera or lens to the tripod.
However, I would agree that if there are some models of camera (e.g. the Leica you mention) that suffer design or manufacturing faults in this regard, then it would be helpful if camera reviews highlighted the problem.