Why has it been disabled? Does this apply to all phones or just the SGS2? Got a MI-ONE Plus here, running 2.12.7, and I also can't move apps to the SD. Not sure whether the function worked before as I didn't try it until my phone started getting full.
I've tried to enable this function via bools.xml but it didn't fully work. But there's no problem for at least Nexus S and N7. I have 1gb internal and I've never got full. And games are installed on 16gb memory in android-secure directory.