Yeah if he says the flange is too short - by 3mm almost! Then this lens has been screwed with already in some fashion. It should have the same register distance that all leica (and Russian) stuff should have - 28.8mm. Leitz specify the tolerance for the correct flange distance as +0.015mm / -0.005mm IIRC. So you can see how far off from usable this lens is.
Anyway, where the Russian lenses differ is that their standard focal length is 52.4mm versus 51.6mm Leitz standard. This means a well calibrated (not all are) Russian lens should be fine at infinity and then increasingly lose focus as you get closer. The focus will be increasingly to the back of your subject, and this is exactly what a good copy will do.
This focal length, by the way, is not just a feature of Russian lenses. Heck even Leitz lenses have it - they used to engrave the FL actual on the barrel for early Leica lenses.
I have a Canon 50/1.8 LTM version II, which of course was intended for use on Canon or Leica rangefinders following Leitz' standard. However the lens focal length is slightly too short. Canon "solved" this by making the shim (flange distance) a fraction of a millimeter smaller than it should be; thus compensating for front-focus as your subject gets closer. This means at infinity, or far distances, the lens overshoots a little bit and gets better as you focus closer. On film this "hack" is not noticeable. Even in film tests at full aperture I never saw an issue, because focus on film is "squishy". It did throw me for a loop when I put it on my (28.8mm calibrated) digital camera, though!