Fog does not work in the sky when using a cubemap skybox

Partner Rank: 2

Verification builds: 1.17.2, 1.17.20
Regression builds: This has always been an issue

Summary: When using custom fog with /fog, it does not render in the sky whatsoever if you're using a cubemap skybox. This means a huge obvious discontinuity between the ground color and the sky color, and you can literally see chunks popping in before your eyes.

Impact: Fog looks so bad we'd rather just not use it.

Repro Steps:

1. Download and open the attached world.
2. Push the button on the command block and wait for the fog to apply
3. Walk in the direction of the arrow on the ground

Expected Results: The sky is basically pure green, because of the strong fog.

Observed Results: The fog is completely ignored in the sky. You can see chunks load in extremely obviously as you walk, since only blocks are properly affected by the fog.

Screenshots/Videos attached: Yes