On an iPad Air, if I launch the game while the tablet is laying flat on the table, the Welcome Screen appears like this:
In this situation, the orientation of the screen will not reset, even when rotating the tablet.
In general, the screen orientation is buggy. The game seems to prefer a specific orientation when it launches (on an iPad): ie, it "prefers" an orientation where the Home button is on the left. If you launch the game with the Home button on the right (which is my preferred orientation, being right handed), the game will pop into the correct orientation, but the system retains the initial preferred orientation status, as shown in the "active applications" display:
So it looks like the game supports both variants of orientation, but the feature is not implemented 100% correctly.