As an “ambidextrous” scroller, it’s just a matter what you’re scrolling: Are you scrolling the scrollbar down, or the content of the window?

I think regardless of the direction you move your fingers, “scroll down” means the same thing: “scroll to a lower part”

"Scroll down" could refer to the motion of the wheel or the motion of the viewport.

When I scroll down I’’m referring to the active window’s motion. Right now I couldn’t tell you what motion I use. I use a trackpad and mouse.

I thought the same as you until I once got a new Mac and forgot to switch off natural scrolling during the initial setup. You scroll down on a page far more often than you scroll up, at least in my day-to-day. Natural scrolling on the mouse wheel makes scrolling down an easier motion on my right middle finger than with classic scrolling. It's easier to push out than to pull in.