Yeah, but that's a slightly different scenario – they a lot of developers on staff already know how to implement private message functionality, and they have better expertise on staff than SnapChat do for the difficult part - getting the UX right. Here, just one guy was doing this a very sophisticated thing that was clearly out of the reach of Apple's developers (SnappyCam came out long before iOS 7, but the new in-house iPhone burst functionality doesn't work half as well as SnappyCam's).