OK, back after testing with the right component.
Using FreeMill, I tested a large bunch of .nc types, and no luck, either with the C: component or the G-code input component.
I can see obvious reasons for it not to work ; most of these :
-do not put empty spaces between coordinates
-do not put all the coordinates on each line ; if a coordinate (Z generally) is constant throughout many points, the Z value will be given once only
-Some add a "N value" on each line
Now, KUKA|prc being within the Rhino ecosystem, wouldn't it make sense to add a "Output postprocessor for..." RhinoCam or MAdCam which are Rhino plug-ins ?
Not sure about MadCam, but RhinoCam at least has a free version.
Or maybe, instead of making a CAM program-specific post-processor, why not make the "G-code import" component compatible with a very popular post-processor which is likely to be found in most CAM programs ?