You can still observe a related effect to this in Windows 10. Open up any large(ish) file in NotePad++ or most any other editor and place the cursor in the text and drag to the bottom of the screen so it starts scrolling. If you hold the mouse still at that point it will scroll through a couple dozen every half second or so, but if you wag the mouse side to side it will scroll through hundreds at a time in the same span.

I always assume that it's because the apps simply scroll on both timer events and mouse move events. Wiggle the mouse to raise a bunch of mouse move events and you get faster scrolling.

every time I use this trick, I think of how running diagonally in some games is faster than running in one direction...

I think that's just because those games are written poorly and don't account for the differences in moving diagonally. If you are moving on a grid, moving forward one tile moves you the length of a tile. Moving diagonally one tile moves you sqrt(2) ~1.4 tile lengths.

More often it is because both inputs apply some speed. Like in doom.

https://doom.fandom.com/wiki/Straferunning

always normalize your input vectors!

Yeah people always look at me like I'm crazy when I do that, but it really does work