I've changed this wording because it's no longer relevant to this patch. This patch doesn't add anything for disposing of layers, that will be coming in a separate patch.

To start to answer these questions though - if a repaint boundary disposes its layer, it means that repaint boundary is going way and won't be drawn again without getting completely recreated/repainted. And so if it has any child repaint boundaries that have not been moved to some active part of the tree, they will not get drawn again either unless recreated/repainted.