An account being required for an online-only game, or the online component of a singleplayer/online multiplayer game, I don't see as being DRM. Whether an account is strictly necessary is another matter though, it may be something required by design (such as an inventory or unlock system) or completely extraneous. And whether or not any game that requires an account for multiplayer content belongs on GOG is a topic I'll stay out of (The Witcher 3 and it's Gwent minigame was entirely offline and contained to the save file(s) on your computer. The multiplayer Gwent could not exist in its current form without the online save).
Multiplayer notice: In order to access the multiplayer portion of the game and unlock the "Ivan" character, you must set up a Wargaming.net account via the in-game interface.
Singleplayer content/unlocks requiring an account, I'm not sure how exactly to classify that. Maybe not DRM in a strict sense, though certainly questionable.