Lighting/worldgenerator issue: black patches and dark spots appearing in the world

The bug

Starting with snapshot 19w02a, there are pitch black patches and dark spots quite commonly in the world, mostly in the plains biome. I haven't seen these in any other 1.14 snapshot that includes the new lighting system introduced in 18w43a.
I could imagine that some of the new code has been reverted to improve performance.

How to reproduce

1. Create a superflat world with the Overworld preset:

   minecraft:bedrock,59*minecraft:stone,3*minecraft:dirt,minecraft:grass_block;minecraft:plains;village,biome_1,decoration,stronghold,mineshaft,lake,lava_lake,dungeon
   

2. Fly around
   → You will find lakes with black patches and dark spots in a minute or two

Addendum

Now that I dug deeper into it, I think this is just a reappearance of MC-29490 which got fixed in 18w06a when the new world generator has been introduced.