Time4Tea: I think the problem is that there is no universally-agreed definition of what 'DRM' is, which is where the ambiguity arises. If you use the definition that DRM is "any content that is locked behind a remote connection" (which I personally agree with), then your interpretation above is consistent with that and a game with locked cosmetics is DRMed.
However, some others seem to be using a different definition that DRM is "something that means you can't play the game". So, they would disagree with your interpretation based on that: that locked cosmetic content is not DRM, because it doesn't stop you 'playing the game; therefore, a game that has only locked cosmetic content is not DRMed.
Seems like I ought to butt in and remind this thread of another definition, which I maintain is the one generally used by the media & games industry at large.
In over 90% of cases (by my admittedly flawed estimate) this definition can be simplified as "anti-piracy technology".
Meaning any technology whose
purpose is to fight piracy, or more generally, to protect copyrights and other rights arising from deals between those who sell the product. "Purpose" here being an operative word.
Meaning that by this definition, you can't determine if something is DRM without considering
why it's there.
Something like Securom, which has come up in recent discussion, is a textbook example of DRM by this definition, because it's main, and really only, purpose is to fight piracy. So there could be no question that a game that contains remnants of that system, by this definition, is not 100% DRM free.
While a game that requires an online server to play is not inherently DRM'd by this definition, even if taking down the server would lock you out of the game. It can be, if there is also a system in place to check that you're a legitimate user.
I'll grant that like any human I'm not perfect and my life experience is limited, so I could have a skewed view of how the industry at large uses the term. Assuming I'm not too far off, I'd argue that this is the closest we have to an objective definition. But at the same time, I'm not all that convinced that GOG has been adhering to it.