Damn. The "iPhone last setup or erased on ..." is really nasty. What can a user really do about that? I feel like this should be fudged somehow by the OS.
Maybe I'm being really thick, but why is this information that the OS would make available to apps?
Is the threat model tracking across multiple apps to correlate what you're doing? In that case, a single app wouldn't show you the fudging.
Seems like in general the iPhone was not designed to avoid fingerprinting from installed apps. Only protection would be avoid installing apps and use the web browser when possible.