So the actual DLC update was just shy of 500MB on Windows. Once you’ve gone to the Steam Store to register / download the DLC, you get another 2.9GB (yes, GB) patch or so.
There’s got to be stuff in there. Unless it’s just Steam re-arranging file contents on disk (again)?
Raising this because I’m a developer and a nerd for details, but also because the extra 3GB download might be news for some.