Probably an obvious question, but did you select the correct orientation when exporting the ipa from the IDE?
When launching an IPA it takes a little longer to pass control to AppGameKit than it does Android. Therefore the orientation is set based on the selection in the export process initially, until AppGameKit has control and hits your 'SetOrientation' command. For Android, as control is passed to AppGameKit almost instantly, there isn't really a need for a splash screen...
What I do, is load my Splash Screen in my AppGameKit code (do it first thing, and then perform a Sync()). This allows me to determine how long I want to display it, and also add any transition if I want to (like fade out)... As for the iOS Splash Screens, I simply use a plain black image. Initial orientation does not matter by doing it this way, and then once AppGameKit has control, I load my own splash screen and set the correct orientation...
Using AppGameKit V2 Tier 1