If your data is lost, you can at least come back to complain,
If you keep clean backups yourself, that shouldn’t be a problem.
If your data is leaked, how will you find out and when? By the time you find out, it’s usually too late. So yes, the former is totally preferable to the latter.
@Lag! This isn’t for fighting stolen phones or anything like that, so easy to wipe phone isn’t a problem. If the phone repairman does this without asking, then you are already having problems, but at least these are visible problems. This is not a data breach.
How easy is it to get out of this sandbox and still get access to other accounts (what about encryption?), well, that’s a good question. But if you can simply press a button and it becomes a lot more difficult for mischievous people… So instead of “Oh, I can see this folder with pictures, take a look ‘against’, ‘This is locked, nothing we see, we go on'”, and sure, You’ll probably have smart people who can beat that, but that’s another step forward.
I already see the point of this feature, even if it turns out to be pretty much “security through obscurity”.