That would be a twist on the disc quality/jitter measurements- in theory (and most measurements) pressed discs will have less noise (jitter) than burned discs. In and of itself it means nothing- the measurements can be replicated by heat, a badly calibrated (including knocked) laser, a dying laser diode, vibration, a bad motor/clamp, the 360 not being level- wobble in the disc, wobble due to bad pressing (it happens more often than you care to know), scratches; dirt and grease on the disc and I could go on and on listing causes. Indeed about the only thing I would really note is a buffer under run- while protection will save your disc as far as a PC drive is concerned it will not necessarily save your disc as far as the 360 is concerned. I am of the opinion here that if it works OK on the 360 then carry on.
Similarly jitter is part of the nature of drives and one of many things that was accounted for when first making them (or indeed not accounted for hence the early/cheap drives as well as console drives being useless or touchy about media) as well as being applied in these very circles (you can read about security sectors and angles elsewhere (ABGX360 startup screen being a good start) but by the time the 360 proper sees them they will have been tweaked a bit so as not to have the exact same angle every time- replay attack).
This variation of the theme is that a burned disc will naturally cause higher levels of jitter (an older paper but a valid one none the less on the subject
http://www.optical-disc.com/techpapers/Jit...tomeasureit.pdf ) than pressed media so the theory is while in and of itself it means nothing a large change between games would say to MS that it is a copy. I say the conditions are far from controlled enough for MS to make that call- scratches, grease, lasers, heat, angles, bad disc pressing and so on.
As for unplugging the 360 does have offline monitoring capabilities.