Why it is here

Let the platform
do the work.

A custom slider is usually where accessibility goes to die: someone rebuilds one from pointer events and the keyboard, the screen reader and the form semantics all have to be reconstructed by hand, badly. This one keeps the real element and makes it invisible, so the parts that are hard to get right are simply not reimplemented. The figure does the same trick one layer down — the wheel’s arithmetic is handed to the style engine, and script is left with nothing to say except which numeral is current.

Both mechanisms here refuse the obvious shortcut. The slider keeps a real input and hides it rather than rebuilding one from pointer events, so the keyboard and assistive layers come free. The figure hands the arithmetic of its own motion to the style engine, so script only ever announces which numeral is current.