Gog makes the offline installers not Larian and 3 days is nothing... its a big change
Maybe (or they gave Larian the means for it?), but even then GOG can only make them if the devs deliver the necessary patch files, and we don't know if that's the case. Thus, an official statement about that here or on the GOG forum would be nice and professional.
From the
GOG Developer Docs:
Offline (backup) installers are automatically generated on our servers after you publish a build to the Master branch. Because these installers are queued up for generation and publishing, there may be a delay of several hours between a build being published on the Master branch and an offline installer appearing in the game library.
This is why the full game's offline installer is usually out shortly after it goes live. Offline patches take longer to build and they have to be tested before releasing.
The full game and updates are available on Galaxy as soon as they're published, in pretty much the same way Steam works. There was initially an 11GB update in Galaxy when this version went live, but something went wrong. I don't know if GOG or Larian messed it up, but the 11GB update was failing and forcing it re-downloaded the whole game. It wasn't up long before it was caught, and the new "patch" everyone was getting was 124GB, which is basically the whole game.
3 days are long if you can't play with your friends on Steam anymore because they already got the update. This busted our weekly gaming session yesterday. And since there were tools to create patches autmatically by comparing the differences between two versions decades ago, I take the liberty to presume that the extent of the change shouldn't matter that much. But again, we don't know, so I'd be happy to be better informed and eventually corrected by an official.
Disclaimer: I don't blame anyone (yet), we just would like to hear some estimate to know if we can expect a patch until our next session next sunday.
Your friends should be able to downgrade to the previous version through Steam so you can continue. For the future, tell your friends to disable auto updates so you can continue playing until everyone can get updated.