Ken Burn Effect on SE2 Slideshow

You cannot change the details of a Ken Burns slideshow on an iPhone, just the music and the tempo. (View photos and videos on iPhone - Apple Support)

That is right. The stills are only moving in one direction. When I am holding the iPhone in Portrait orientation, the stills are moving to the right, when I am holding it in Landscape orientation the stills are moving upward.

But there are no controls at all to change this behaviour.