Not sure what aspect of lens performance is being wiped, but I'm not surprised, having used the ZM 35/2 for a couple of years now and the 35/2.8 for a shorter period as well. The ZM 35/2 softens at f2 (very clear from its mtf chart). Assessing the worth of the ZM 35/2 only at f2 isn't necessarily a balanced assessment unless you shoot only at f2, obviously.
In my experience, by f2.8, the ZM 35/2 looks very much like the ZM 35/2.8 wide open in terms of sharpness, color, and contrast. Bokeh's not at the level of the c-biogon's (which is remarkable to my eye), but it's very good. The ZM 35s image very similarly, imho. And judging from the poll, since the Nokton doesn't wipe the floor with the c-biogon, it wouldn't do so with the 35/2 (beyond f2 anyway).