You, as 'someone who probably should know', confidently stated that, in the USA, controllers routinely query non-mode-C VFR paints as to their level. When pressed as to how they did this (or how we would in Australia) when the pilots were not on the ATC frequency, the discussion suddenly dried up.
No, it didn't dry up. As I ahve posted here and everywhere else, I currently do not support the 'no monitoring the freq' policy in E.
I continue to put my point of view to AOPA and Dick Smith. I am there, like here, only one voice.
AK