Why would it be different than on an iPhone where it is available? If anything there are more potential fluctuations with the phone given all the other cell radios and signals to always account for which change more often than just WiFi that's on the iPods.My only explanation, is that it doesn't work quite properly. I used to enable it via .plist hack, and both on my 2nd gen and 5th gen iPod touch, the number would go up and down wildly depending on my usage.
It was close enough though, to know when it was going to die....