Earlier quoted context omitted.
That's commonplace in audio production programs/plugins actually.
Was going to say. It saves screen space - should you need to save screen space - while allowing fine control. A slider would take much more screen area. This is a bigger issue on synth VSTs that have tens or hundreds of controls. When screen resolutions were smaller it was a toss-up between hybrid vertical/rotational scrolling, horizontal/vertical window scrollbars to get the controls to appear at all, and multipage…
Humans are terrible at reading angles quickly.