[…] but I assume it's more the developers/publishers fault than GOG's, isn't it?
Yes it's entirely up to the developers to push updates.
GOG only has a 24 hour testing period which after the update get's accepted (or rejected if there are problems with it).
It's GOG's platform with GOG's rules. Obviously, GOG were in touch with Orwell's developers before releasing Orwell 2. This would have been a good opportunity to insist on the update.
Moreover, Orwell: Ignorance is Strength considers some of the player's choices made in Orwell 1. Changelog for 1.2 says that savegames are no longer compatible. Therefore I consider this as a serious issue. I don't want to augur on whom to blame, but from a customer's perspective that's certainly not my duty to sort that out.