Agreed. Personally, I wouldn't be interested in spoiling the game, but let users have this option is they want to.
Reading the threads on Steam, apparently the game checks your internet connection at startup, connecting to google.com. There are already people who unfortunately can't play the game because the game doesn't detect a connection.
At this point I think the delay for the release on GOG is due to the removal of this check in the GOG version of the game. In any case I hope it won't take long, because the concept intrigues me a lot.
Pretty much, I posted this in the GOG forum for the game and I agree with you, it must be the reason. https://www.gog.com/forum/the_longing/release_delay_on_gog/post2
"I suspect it is to remove the requirement to be connected to the internet to start the game, which goes against GOG's DRM free policy.
..."Luckily, the game only needs to check once on startup, so no constant internet connection is required. " https://steamcommunity.com/app/893850/discussions/0/1638668568128088208/#c3681064390585350952
If you look at the profile who posted this, it is clear that it either a developer, or someone working for the developer. This requirement breaks GOG's DRM free policy. " Why buy on GOG.COM?
DRM FREE. No activation or online connection required to play. "