Using adb, "adb reboot bootloader" or "adb reboot-bootloader" just makes it reboot normally.
From a shell, doing "su reboot bootloader" also reboots normally.
I tried Quick Boot from Google Play which has an option to reboot into the bootloader, but it also just ends up rebooting normally.
While powered off, I tried holding power and volume up, power and volume down, and power and both volume up and down, but they all just boot normally.
Doing "adb reboot recovery" does boot me into recovery mode, but the menu doesn't have a bootloader/fastboot option.
Does anyone have any idea how to enter the bootloader/fastboot mode for this tablet? Any help would be appreciated.