As far as I understood @Tom, the small space is meant to be the minimum required space to make it not cramped and the worker can still walk around and nothing wrong with it to place it in something bigger and the likes like @Andarvi said.
In addition, the “workshop” is important for promoting people. If you not have certain tools which would define the workshop, you can not promote someone to that job. In case of the carpenter, you would need to define the input and output areas and have your workers collect 2 or 3 logs for the working benches.