So when I go to create a Superflat World in Creative Mode with the Redstone Ready preset, it hangs, roughly at 15%. The only way to exit is to force stop the game. When restarting the game, the world that should've generated is shown in the listing (as though it did truly generate) this then hangs at 4% loaded.

From looking at the launcher_log, it appears I am getting the "Unable to find spawn biome" bug, however, unlike how that bug is portrayed, there is no warning, it just continues to sit, possibly forever.