When people say “I own the game” these days they are generally saying there is no DRM or other factor preventing their passing it around for whatever reason

That’s why I said:

If it’s actual ownership instead of availability

The context is that the person I was responding to said they use GOG because they ‘own’ the game, in response to someone else saying that there are games on Steam with zero DRM that you can also buy.

Frankly, with the ‘availability’ argument you also don’t need Steam to play them and could copy them over to a PC that’s never had Steam installed and play them as well.