Operating system: Latest Windows version as of Decembre 2018.
Bug: The 'A Complete Catalogue' advancement is achievable by taming a single llama, without taming a single cat.
What I expected to happen was this advancement to not even be updated after taming a llama.
What actually happened was the advancement did not just go one step further, but all steps were suddenly completed. (Just this advancement)
Steps to reproduce:
1. Spawn a llama and make sure you have not tamed any cats yet.
2. Feed it wheat and sit on it to tame it.
3. the advancement should unlock, I tested it on 3 different saves.