The Bug:

The darkness pulsing effect doesn't appear gradually when in low light levels.

Steps to Reproduce:

1. Ensure that you have the "Darkness Pulsing" option set to "100%" in your accessibility settings.
2. Enter a large area that has a low light level and give yourself the darkness effect by using the command provided below.

   /effect give @s minecraft:darkness 999999 0 true

3. Watch your surroundings closely as the pulsing of the darkness effect occurs.
4. Take note as to whether or not the darkness pulsing effect appears gradually when in low light levels.

Observed Behavior:

The darkness pulsing effect appears and disappears instantly when in low light levels.

Expected Behavior:

The darkness pulsing effect would appear gradually when in low light levels.