Operating System: Windows 7
I used the debug screen in the screenshots so that should provide adequate information
I know village generation has always been a bit unusual, but I've noticed a change in 18w20b that should be significantly bad enough to constitute a bug.
The screenshots below document changes in two villages on seed -1165132418 between snapshot versions 18w19b and 18w20b. The main affects consist of buildings and structures like farms and torches being placed either partially buried like the watchtower in the desert village or partially buried at the bottom of a pit like the library in the desert village. Both have farms that generated almost completely underground.
view of savannah village in 18w19b (above top) and in 18w20b (above bottom)
view of desert village in 18w19b (above top) and in 18w20b (above bottom)