Firefox: When tabbing up/down (and scrolling), window.scrollY registers twice, one pixel apart

Question

When tabbing up/down (and it activates a scroll), the scroll is instantaneous (not smooth) and doesn't land cleanly on one value.

If you put this in the Console of any site, you can compare the different scrolling behaviors:

document.addEventListener("scroll", () => {
    console.log("Scrolled");
    console.log(window.scrollY);
})

Scroll up/down by mouse (Works fine)

• Scroll up, the last print of window.scrollY will be smaller than the previous one because it's closer to the top of the viewport

• Scroll down, the last print of window.scrollY will be larger than the previous one because it's farther from the top of the viewport

Scroll up/down by arrow keys (Works fine, the same way as above)

When tabbing, and it activates a scroll, this is where it works incorrectly

• Scrolling down, the last print of window.scrollY will be 1 pixel less than the previous one (*But NOT always. Sometimes it's okay.)

• Scrolling up, the last print of window.scrollY will be 1 pixel more than the previous one

E.g. Tab DOWN --> Activates scroll (non-smooth)

PRINTS IN CONSOLE:
      3964.2666015625 
      Scrolled 
      4709.2666015625
      Scrolled 
      4708.2666015625           (It "lands" here)

I tested this same thing in Edge and Chrome and they print window.scrollY correctly and scripts work good there.