Summary:

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:

1. Set time to daytime. (sky-light = 15)
2. Prepare water 4 blocks in depth. (sky-light level of bottom of water = 15-2-2-2-2 = 7)
3. Fill bottom of water with glow-lichen. (block-light level = 7)

Observed results:

Drowned spawns on bottom of water.

Expected results:

Drowned doesn't spawn. (because there are no blocks to fulfill the condition)