In Windows mouse “distance” is a system setting, default to 4 lines per click (which I think you can set in settings.) Most games will just directly take in the “scroll up” and “scroll down” button inputs.
If a mouse has a scroll ball, (or is a touch pad), I would guess it uses a custom driver or something (my old laptop did), and for games/software that need “presses” rather than lines, the mouse driver will have its own criteria for what counts as a button press. Your D-Pad driver probably does that too.
I had the broken scroll wheel thing on my old Razer Naga 2014, I think the contact wore out easily. Sometimes when I scrolled it wouldn’t scroll at all, and then suddenly scroll 80 lines at once because it kept on registering the “click”, and sometimes it would even go backwards.