The snowy Kingdom superflat biome spawn abnormal. The snow on y=64, the grassblock on y=-1. This is probably caused by MC-214951.
Blocks of grass are not snowy under snow in superflat worlds
snowy kingdom snow worlds generate too high
Superflat worlds start generating at negative coordinates, causing a dark horizon
Desert temples in superflat generate way too high
Ocean Monuments in Water World presets don't spawn correctly
Some blocks generate at wrong Y height in a superflat world