It sounds like a terrible feature, but it really works in some circumstances. A minesweeper app I had long ago allowed swapping between flagging and uncovering by pressing the volume buttons, and let me tell you, what an amazing feature that was. You could get almost as good times as you could on a PC, it wasn't clunky like most mobile minesweeper apps are. Having to tap a flag/uncover icon to swap wastes a few seconds, and long tapping on a square to flag it is just miserable.