https://drafts.csswg.org/css-color-4/#interpolation-missing

If a color with a carried forward missing component is interpolated with another color which is not missing that component, the missing component is treated as having the other color’s component value.

Therefore, the carrying-forward step must be performed before any powerless component handling.

This is followed by example 37:

For example, if these two colors are interpolated, the second of which has a missing hue ...

But example 37 doesn't have any powerless components.
Neither is there any color space conversion.

For example by the current spec:

color-mix(in lch, oklch(78.3% 0 326.5), oklch(39.2% 0.4 none)) should result in lch(49.61684142 61.33679401 none) where the outcome doesn't have any hue!

I am unsure what the intention was behind the statements or example 37.
It predates a lot of edits, but maybe the aspect it tries to explain is still relevant and just needs to be updated?

@svgeesus