[happytoexplain]

It's a good point - I am not an expert, but I think this feature just doesn't protect memory (tying one of the keys to rebooting helps, but the Data Protection feature itself doesn't seem to protect memory). However, that doesn't moot in-storage protection. There are other features protecting memory (and other features protecting data in storage - there are tons of security features).

I am not aware of APIs for securely clearing your app's memory (aside from lower level, more manual APIs). This may be one of those cases that relies mostly on sandboxing for protection. I also imagine it's hard to circumvent sandboxing without rebooting. But I'm making a lot of guesses here.