I thought you were suggesting a way that meant phone backups all appear the same size as the disk 100% of the time. (meaning the true volume of content is hidden)
Then the second point is the user could potentially have two (or more) profiles on the device, and it is possible to unlock it into one or the other. Meaning a user under duress can unlock a device and not reveal the true content while the person trying to get into the device has no way of knowing if that is the true profile or not.
I figured that would be a pretty sweet feature. It would also tie neatly into allowing users to have multiple profiles on their device which is currently impossible on iOS...
yeah it isn't awesome that we feel we need these security features. However I think even without the fear of government (etc...) this is still a great feature I would love to have.