TechnoMasterDude: I have never benefited from this service anyway, as it has never detected any of my games or even actually worked. I have now further set my privacy settings on Steam to private, as to avoid any sort of interaction between these two services.
There's nothing to avoid.
If you don't go to GOG's Connect page, there's nothing happening automatically.
If you set your Steam settings to private, you can't make them interact even if you tried to.
If you want to make certain absolutely nothing happens anyway, add
www.gog.com/connect
to your blocked URL's list, or make it automatically redirect somewhere.
That way there's no way you can even accidentally trigger any game search process with GOG Connect.
Of course, if you actually connected your accounts in the first place to get free games, I see no reason why you all of a sudden would try to block that from happening.