Where did they get that number? MS stated the attach rate for America was 7.0, and I am very sure the attach rates in PAL and JP would only pull it down.
According to VGC American
360 - 7.5 (includes Forza/Marvel bundle)
PS3 - 5.2 (includes Motorstorm bundle)
Wii 5.5 (inc Wii sports)
without bundles PS3 is probably at 5.0, 360 at 7.0 [like NPD said] and Wii is at 4.5.
So the 8.8 is BS
(If PAL has a lower attach rate than America then it will pull it below 7.0)