I created a Super Flat world with the following preset `minecraft:air;minecraft:plains`. I left structures on as I was wanting to tackle a skyblock type challenge, but with only what's available in a village. When the world generated, none of the villages had any floors, so most of the villages fell and died in the void except two that spawned in a 2 story house.

This also effects the stronghold as aside from the portal room, no blocks were generating for the floors.

I believe this is a regression from previous versions, as I remember the floors generating there.

I've tested this on version 1.18.2 as well as the current snapshot 22w17a. My guess is the system in charge of placing structures is looking for specific blocks to replace with the floor blocks, and air is not in that list. This cause the village buildings to generate, but the air remains causing oddities such as half-doors as well as the aforementioned mass villager death.