In 1.18.0 and after, Drowned seems to spawn in condition [sky-light<=7 && block-light<=7].
Since 1.18.0, I understand as that Hostile mobs spawn in [sky-light<=7 && block-light=0].
- Hostile mobs spawn only in areas where the light level is equal to 0. (This change affects only block-light and not sky-light.)
Surface mobs spawn only in areas where non block-light, as expected.
And in Java Edition, Drowned spawns in non block-light, too.
Step to reproduce:
- Set time to daytime. (sky-light = 15)
- Prepare water 4 blocks in depth. (sky-light level of bottom of water = 15-2-2-2-2 = 7)
- Fill bottom of water with glow-lichen. (block-light level = 7)
Drowned spawns on bottom of water.
Drowned doesn't spawn. (because there are no blocks to fulfill the condition)