When I played Wticher3 on PC the game would always launch the GOG app first which most definitely requires an internet connection. While I'm sure that I could continue to play if my internet connection went down in the middle of the game, I'm also fairly certain that I couldn't start the game if my internet connection was down. And I most definitely can't play Cyberpunk without an internet connect since I got it on Steam, I need to start Steam in order to play and Steam requires an internet conneciton.
Two things about this.
1. For GOG, while you can run everything through Galaxy (or whatever their front-end software is), you can also just run them straight from the executable and it'll skip Galaxy altogether, I believe. The key here is that, I believe, the games don't actually
check to see if you're running Galaxy, nor look for some online handshake.
2. For Steam, while you often (but don't always) need the front end software to run a program, you can run Steam in Offline Mode and still play many games.
Put another way, for a lot of these games you run through this or that software platform, the platform is often not truly necessary (as much as it is "convenient"), insofar as the game's main executable will still run even if the platform software isn't running. And many games don't require an online connection because, even if you're running through the platform, you can still run the game even if the platform can't connect online.
The next time you want to see if a game requires you to either use the front-end software or be connected online, try the following:
A. Navigate to the game's install directory, and run the main executable. If the game doesn't automatically boot up the front end platform, it doesn't require that nor does it require an online connection.
B. If the game boots up the platform to run, close the game, then switch the platform to "offline mode" (or whatever the equivalent is for the platform), and try to run it again. If it runs fine, you don't need an internet connection, but you do need the platform.