Dawnsinger: I hazard a guess that it means "Epic Online Services", probably the stuff that implements Steams suggestion "We suggest enhancing the value of legitimate copies of your game by using Steamworks features which won't work on non-legitimate copies (e.g. online multiplayer, achievements, leaderboards, trading cards, etc.)." in Epic.
https://partner.steamgames.com/doc/features/drm#1 Whereby, of course, every copy that is not bound to the respective client is viewed as "non-legitimate", even though it perfectly may be and simply being run offline.
I can not follow your explanation because if you, for whatever reason, want to play a game online using a client...
in such a case your game is registered on that client and its legitimacy is always verified. DRM free simply means that it can even be run offline without any client in any case... even permanently. Sure, there will be no online achievements or other online traits doing so... yet many users do not want to use those online traits on a "non online game".
The only reason i ever connect online... is if i actually play a online-only game (and of course in order to download a game)... which makes sense to me. I do not care achievements (a achievement can be bound to the game itself, and if someone is connecting, the achievement will be synced with the server... although DRM is usually avoiding this method). I always mod the games myself... without "external help". Steamworks is simply a mod platform and by far not the only one.
DRM is critical even on that matter because some "modders" may even adapt their launcher or manager to the client-environment (they want to be stick to the rules they say and most gamers loving it) which basically adds another DRM-layer... just very ugly... in such a case even foreign "developers" are helping out this platform in order to "cement" this game to this platform forever... instead of making it free.
Its exactly the stuff Google has been doing for a long time already and yes... they are not avoidable anymore, their power is above anyone else, as almost anyone is supporting their environment... the same way devs are supporting the Steam environment... almost exclusively: There can be no better DRM... even Denuvo is weaker than this.
It works exactly like this if people use Galaxy... as this is a optional client.