Smooth Lighting is broken for blocks below Y=0

Summary:- Blocks that are below Y=0, the smooth lighting is broken, even tho Smooth Lighting is turn on.

How To Reproduce:
1:- Enter a world with Caves & Cliffs Experimental Feature Turned On.
2:- Explore the caves below Y=0

Observed Results:-
The extra shading around the edges of the block isn't present, making it harder to distinguish shapes.

Expected Results:-
This should not happen.

NOTE: I turned off all my resources packs. No behavior packs where installed also.