From @whichonespink44 on June 9, 2016 16:30

Original report:
http://minecraft.curseforge.com/projects/realistic-terrain-generation?comment=85

It seems like in RTG-1.9.4-2.0.0-alpha.5 that swamps are generating stone instead of dirt. The seed is -1854747965 and RTG is the only terrain generating mod that I'm using.

Copied from original issue: Team-RTG/1.9-Realistic-Terrain-Generation#127

From @topisani on June 20, 2016 0:25

this is probably just some stupid surfacing mistake

I started looking at this today, and it appears to be using the same surface code as Plains and a few other biomes.

Is it just a case of setting a lower minimum Y for the top block part?

Fixed in 2818720