Not much help perhaps, but here's my observation. I have a 350 cc classic with the standard clutch setup and 4-speed box. I've never seen the primary drive cover move, but to be honest I have never looked at it while changing gear. I just went into the garage and couldn't see any movement when I pulled the clutch in. I put my hand on the cover and tried again, but couldn't feel any movement either. Having taken that cover off and looked at the inside of it in the past, I can't see how it could move unless the clutch assembly was touching it. To make that thickness of metal move it would have to be touching it with quite a bit of pressure and would make a lot of noise.
Or am I missing something?
Tom