What happens to the type?
Press Replay and watch Aa. Resize rewrites the box every frame, so the type reflows. Slide (FLIP) paints the new layout, then fakes the old size with scale, so the letters stretch. Keep type sharp undoes that scale on the letters.
What changes is the new layout. How it moves is Resize, Slide, or a cut. Keep type sharp only appears when Slide grows the box.