The usable, parallax-corrected, frame line based optical viewfinder, alon with the parallax corrected OVF focussing make this a "rangefinder camera".
That, and sensors and lenses that can actually compete with a 'real' RF.
Nick, I just replied on the first part of this argument for describing it as at least a "rangefinder-like digital camera"; there is something to that argument that some part of the RF experience is preserved.
Your second sentence does not persuade me; partly because sensor and lens performance are nothing to do with why people would call a camera a "rangefinder", but mostly because I am not convinced that the sensor and lenses are really so much better than the various sensors and lenses for the other new compact digital camera systems (not at all to say that they are worse, or not good: your samples look fine!) In the realm of fixed focal length lenses, here is what some of the recent compact systems offer, considering only lenses that work with the cameras' AF systems and excluding adaptor-mounted lenses like 4/3 SLR lenses on m4/3 bodies:
Olympus and Panasonic lenses for Micro Four Thirds mount:
8/3.5 fish-eye, 12/2, 14/2.5, 17/2.8, 20/1.7, 25/1.4, 45/1.8, 45/2.8 macro, with a 60/2.8 macro and 75/1.8 recently announced. (Also a couple of third party AF lenses: the Sigma 19/2.8 and 30/2.8).
Sony lenses for NEX mount:
16/2.8, 24/1.8, 30/3.5 macro, 50/1.8 (with fish-eye and ultra-wide converters for the 16/2.8).
Samsung lenses for NX mount:
16/2.4, 20/2.8, 30/2, 60/2.8 macro.
Fujifilm lenses for XF mount:
18/2, 35/1.4, 60/2.8 macro.