Lifthrasil: Courts don't start cases. You need someone to sue GOG for false advertising first. Someone with enough money to fight such a law-suit through multiple instances. GOG was careful enough not to promise 100% DRM-free anymore. They just say, that GOG is the home of curated DRM-free games. Promising "a selection of DRM-free games". ... Which they do. A selection of the games on GOG is still DRM-free.
Moreover they promise: "Here, you won't be locked out of titles you paid for, or constantly asked to prove you own them - this is DRM-free gaming." ... which seems to promise completely DRM-free gaming, right? No, it doesn't. It shows what their definition of 'DRM-free' is in legalese:
1. you won't be locked out of titles you paid for. - Which means DRM on Gwent is OK and also extra content (DLCs) and so on can be locked behind DRM. You still don't get locked out of the base game you paid for. So from a legalese standpoint GOG is in the clear.
2. you won't be constantly asked to prove you own the games - which leaves the door open for occasionally asking you to prove you own the game. As long as it isn't constantly. ... I.e. if you read this with a legal goggle, all this sentence does is promise not to use always-online DRM.
Nowhere does GOG promise nowadays not to use online-registration or to keep all parts of all games DRM-free. They have carefully reworded their 'about us' page towards becoming a DRM-agnostic platform. That makes suing them very difficult.
The only thing that might still be seen as false advertising is the promise, that Galaxy is optional. Which is still there on the 'about us' page. However, even there they removed the '100%'. They don't promise anymore that Galaxy will always be 100% optional. So it's a grey area. They still call it optional, but for many multiplayer-games and some single-player content it isn't. So if you have the funds and time to sue them over false advertising, this might be an angle. But expect a long fight.
There are some other things they promise that look like false promises, because they imply a quality of service that just isn't true. But if you look closely at the wording, everything is so vague that it won't be persecutable in front of a court.
Lifthrasil: And so on. Their lawyers did a good job re-wording their promises in a way so that they don't actually mean anything.
I dont agree with your implied assumption that 'word games' (misleading deceptive advertisements) give them legal safety. Far as I know about such things its pretty much a dice roll whether they would get away with it or not in a particular case. Thats also what I think is the motivation behind the rewordings. Not as you imply this making them 'safe' but rather increasing the odds of getting away with it if they somehow get sued over it.
it says "DRM FREE. No activation or online connection required to play."
From my POV there is no way this would hold up. GOG: "Yes 'DRM free' means only a part of the game needs to be 'DRM free'" - I dont think so...