I don't understand why Apple instead of just deprecating the UDID API did not added at the same time an API returning an application-specific UDID. No privacy problems, no issues for developers.
Such a thing has existed since iOS 2.0 (CFUUIDCreate [1]), and Apple's updated docs on UDID specifically recommend using CFUUIDCreate. The problem is that an application-specific UUID doesn't address all current use cases for UDID. Specifically, ad networks that support Cost-Per Install (CPI) need to use an identifier that crosses the application boundary.
Perhaps I misunderstood, but CFUUIDCreate doesn't create an application-specific UUID, it just creates a new, arbitrary, UUID that isn't tied to anything. You could then use that to build your own app-specific UUID mechanism, but the API won't do it for you.
It's relatively straightforward to use CFUUIDCreate as a building block for an application-specific UUID, but you're correct in stating that the API itself simply returns a new, pseudorandom UUID.
For what it's worth, I filed a bug report for this a while back and it got closed as a duplicate. Hopefully it's something that is coming before they remove the UDID method.
[1] https://developer.apple.com/library/mac/#documentation/CoreF...