Why can only floor cutouts be resized?

Hi! I'm wondering what the difference is between a floor cutout vs a wall cutout or a counter cutout. Basically I want to know why in-game items like the in-ground onsen pools (snowy escape) and glass floor tiles (island living) can be resized in game even though they have floor cutouts. But we can't resize things like windows, doors, and sinks, because the cutout stays the same. What is the difference? And is it possible to make a cc window or sink that can be properly resized in game?

Thanks!