Nice to know. But if you are offline those games works anyway ? There is any sort of authentication/protection or you can copy as you wish ?
If you are referring to the part about
"Also lots of steam games run from the download folder without any need for steam any internet and without any check", that's going to be dependent on the game. If the developer/publisher of the game decided to include Steam's built-in DRM, then Steam will need to be running for the game to launch, otherwise if they chose to not utilize Steam's DRM, you will likely be able to launch the game directly from it's folder without starting Steam. They may or may not choose to utilize other DRM though. It's the same on some other services as well, like Epic Game Store, where many titles can similarly launch without the client running. It's probably more common with games from small developers and older games though, as publishers of AAA new releases tend to be more likely to use DRM.
You would have to test to see if a particular game is able to launch that way though. Or there are also some lists of games that can launch without Steam that you could reference, though they are likely missing some entries. This one for example, has different sections for games that can launch directly without any additional changes, those that simply require you to make a "steam_appid.txt" file containing the game's app ID number, and those that may require other workarounds to launch without the client running. Just hit the "Expand" link under a given category, and a long list of titles in alphabetical order pops up...
https://steam.fandom.com/wiki/List_of_DRM-free_games