Again, I’ve read the patch notes and the FAQ. That’s not what it says. What it says in admittedly a convoluted way) is that you will need 44,5GB free over your existing install of 40,5GB, for a total disk space required during update installation of 85GB, to install a measly 4,5GB patch.
What they are doing, and they explain this in the FAQ, is that you download the 750MB patch, make a copy of your original install (40,5GB), uncompress the patch (.-750 MB + 4,5GB) and apply that patch over the original install keeping the copy in case something goes wrong (-2GB total since there will be some overwritten files).
Needing 85GB over your original install would mean copying the game, then copying it again, applying the patch over the second copy, use that copy to overwrite your original game, and do nothing with the first copy or your original files. It makes no sense if you think about it 2 minutes.