I haven't played for over a month, got in the mood to start a new playthrough only to see that the latest update requires over 100GB. WTF is this? Is it literally reinstalling the entire game or what? If this is going to happen after every new patch then I guess I will have to stick to my current version of the game because 100GB just for an update is unreasonable.

yes pretty much its installing the entire game because all the files have changed in those last few months

honestly you are better off doing a fresh install of the game than a update and no its not anywhere near ready yet... act 3 is still a busted joke you are unlikely to finish

my understanding is, it's a gog issue this doesn't happen with the steam version, don't know about the ps5 version.

It is the same for the Steam version

The patching process | Patch deletes the game explained
https://steamcommunity.com/app/1086940/discussions/3/3958162152960089964/

your understanding is wrong

only the off line install is a Gog issue but also as a side point this thread is about a different patch to the current one

Seriously. WTF is this? The last two patches have been well over 100GB, downloaded slowly (takes several hours on a fast connection) and FAILED at least once each. As far as I can tell I am better off uninstalling the game completely and then reinstalling it every patch rather than rely on GOG patch downloader to sort this out.