Will have to check later today or this weekend. I'm running Minecraft Overviewer against a backup of the world to generate a map; there is one village I noticed that is only half generated - we were close enough to it for a few houses to appear on map but we didn't see or explore it - so going back there to let the remaining half of the village generate would be a good test. Before 1.13 came out I used mcedit to manually delete the oceans and prune some lightly-explored chunks. I saved the Overviewer map of the 1.12 world, I know there are at least 2-3 villages on that map; they should generate in the same region if re-explored now. That would also help determine if this is a random coincidence or not.