I've captured dmesg output from a Win->Ubuntu restart and then booting to Ubuntu from cold. The way that USB is handled is quite different: Bluetooth is not started after restarting from Win, uvcvideo is handled differently and there are a bunch of other little differences. I'm not sure which of these might be significant, but it makes the difference between being able to suspend and not.
I've captured dmesg output from a Win->Ubuntu restart and then booting to Ubuntu from cold. The way that USB is handled is quite different: Bluetooth is not started after restarting from Win, uvcvideo is handled differently and there are a bunch of other little differences. I'm not sure which of these might be significant, but it makes the difference between being able to suspend and not.