It will be very interesting to see if my box will get banned too. It originally had an ms-28 drive which was first flashed with Xtreme 3.3 (reports as ms25) before the fall update. When the 5.x fw was released I tried flashing that, almost bricked the drive, replaced it with a flashed Hitachi drive until the ms28 was fixed and now it has the ms28 back in it with Xtreme 5.3, which reports as ms28. I never went online with it from 2 months before the fall update onwards, I did not apply the fall *or* the spring update, never played a backup online (never logged into live with one in the drive), but I *did* flash it with the DVD powered by the 360, and I *did* download XBLA games with the Xtreme 3.3 fw flashed to it and maybe even with the flashed Hitachi (don't remember).
So atm I have a 360 that might have some red flags logged in flash, but which is not banned yet, still on kernel version 2585 and never had a backup in the drive while on XBL. For now I will not connect it to XBL until the new fw is out, but I'm really curious if MS can ban this one as well...