update: I found that while previously visited areas/chunks are still the same, newly generated chunks are normal i.e. the new chunks look like a normal world with biomes, caves, etc.
If you build a snow golem and make it throw a snowball at a iron golem, after the iron golem has killed the snow golem it will stand where the golem died, flailing its arms.
Benjamin Chiu
update: I found that while previously visited areas/chunks are still the same, newly generated chunks are normal i.e. the new chunks look like a normal world with biomes, caves, etc.