This demo outlines the biggest challange for me for scroll-buttons as DOM elements. If and when an element overflows and thus might be in need of scroll-buttons and other scroll related UI elements is highly dependent on css layout, container and page dimensions as well as actual content inside the potential scroll container.
This Container should be scrolling horizontally on every device.
This container only becomes horizontaly scrolling on devices smaller than 620 px
This never scrolls, because there are not enough items inside.