OK. Again artificial limitations on "older" hardware by Apple.
Greedy company Apple.
Wow. Both devices have 4 gigs of RAM. So then it is about the processor. Maybe, since A10X has three high-performance cores, they are dedicated to the 3 apps on the screen. A9X has two cores. They could’ve made two apps still running and one app greyed-out, but I believe they avoided it to prevent confusion. Still, greedy movement.