none vs 0 – when are they equivalent, and when not, in CSS color functions?

I’m trying to understand none vs 0 in CSS color functions by creating some visual examples in CodePen. My current understanding is that, at least in practical terms, none and 0 are equivalent except when interpolating between colors of different spaces. When setting the value for a single, static color, none and zero should produce the same result on screen. See the MDN docs here.

But I see at least one exception to this, where zero outputs color and none outputs black. These two values produce visibly different results on screen:

lch(none 90 0) vs lch(0 90 0)

div {
  display:flex;
  flex-grow:1;
  height:50px;
}

<div>
  <div style="background-color:lch(none 90 90);"></div>
  <div style="background-color:lch(0 90 90);"></div>
</div>
<div>
  <div style="background-color:lab(none 90 90);"></div>
  <div style="background-color:lab(0 90 90);"></div>
</div>

Same for lab(), which shares the lightness parameter. But it doesn’t apply to the hue in lch(), at least not in Chrome. In Firefox setting hue to none sets the output to black, so one of them is wrong…

This example indicates that none and zero are different beyond interpolating between two separate colors. Can someone please clarify that, or point me to some docs that explain it for dummies like me?

Also, what are some specific examples where interpolating between two colors produces different results with none vs 0? I am using linear-gradient() as my interpolater for test purposes, and I am having trouble finding cases where none vs 0 makes a difference in the interpolation of a linear gradient.

Edit: after posting this question I saw that the example snippet displays differently in Chrome vs Firefox – the left and right sides visually (none vs 0 in the CSS) are flipped between the two browsers.