I’ve noticed this subtle touch in Photos on iPad (and iPhone) before, but I guess it never really registered. I was thinking about it last night, and I realized it’s just the kind of thing that Apple pays attention to and does well.
When you’re flipping between pictures, notice that there’s a gap between them. It’s deliberate—and most people wouldn’t think to add a space there.
It’s totally unnecessary, but once you notice it, you realize that it looks so much better than letting the pictures bump up against each other.