So I was trying to generate a superflat world using the preset "3;minecraft:bedrock,10*minecraft:dirt,minecraft:grass;1;village" (the seed was 4954562771710720398) and it turned out CRAZY.

I spawned next to a village and a large area about 3000x1000 blocks full of GIANT DIRT PILLARS.

I can't explain it more than that. Look at the pictures.
(map.png is a view from the top)

I then recreated the situation again as best as I could and they were gone.

Any ideas why it would behave irregularly like that? Or at all?!?