I have opened two different superflat Minecraft worlds in survival mode with cheats disabled and the bonus chest on, and in the first world (which used the Overworld preset) I went to five different villages with no sign of a blacksmith shop in any of the villages. Thinking it was a bug with the world, I tried a second world (this one was default superflat) and went to a couple villages, but there was still no sign of a blacksmith shop. These two worlds use the same seed, which was "give me a village pls." EDIT: Another village I went to in the second world had a blacksmith, but I feel like this issue is still worth reporting.