After a spawned or grown villager touches a workstation to change to the profession, if you break the workstation soon after, the game will crash. Whether instant, or seconds after. As far as I have tested, the longer you take to break the workstation, the longer it will take to crash. (wait 5 seconds, it will crash 5 seconds later, break it instantly, crash instantly).
If the world saves after breaking the workstation, but before the crash, it will break the world permanently.