Smooth lighting has brighter outlines

The bug

in 21w10a the option smooth lighting looks different / worse than in 21w08b

21w08b:

21w10a

How to reproduce

1. Generate a flat world
2. Make a 20*20 platform above you e.g. by using /fill ~ ~25 ~ ~20 ~25 ~20 stone
3. Compare 21w10a with another version
   in 21w10a there is a bright ring around the dark square