It just needs to be "owning* in the way physical media without DRM works. That is data too after all. The ability to sell your copy of the data or have your friend borrow.
Yes, DRM-free is the closest thing, never argued otherwise. I’m also not arguing the services offered by GOG are part of “ownership”. The lack of an ability to download a game at any point is just a part of the fact that GOG too is simply licensing in the end. But yes, GOG is still the closest thing to “owning” games. Which is why it sucks that so many titles on GOG have DRM despite the claims btw…
I’m really only arguing one thing: piracy is better than GOG right now in every single way. You don’t have to worry about hidden DRM. You don’t have to worry about account creation bullshit. You don’t have to worry about anything else. You just download, hit play and it works every single time. If I send the copy to a friend, it will still work.
Piracy has always been closer to “owning” than GOG, so GOG should at least have some other tangible benefits over piracy. But right now, they don’t.