The bug
Superflat worlds created with the Tunneler's Dream preset are generated with snow on the surface. That was not the case in previous versions.
Original description
When I try to make a Tunneler's Dream superflat world, it loads me into a Snowy Kingdom superflat instead. (Latest seed: -6780918275031299935) It's been this way through several patches now.
Can confirm. But, the issue here is not that the snowy kingdom preset generates instead. The issue is that a layer of snow is being generated on the surface. As the world is quite high up and in a mountains biome, that might be intended.
I edited the ticket a bit to reflect that.