I wouldn't consider, having to be online to play an online game DRM. If they provided an offline mode, but you still had to be online to authenticate the game throughout, that would be DRM (and bloody stupid), but the online solo isn't DRM.
In effect that's precisely what Solo Online is, within reason. It's an offline mode but with the caveat that you're constantly authenticating and validating your actions every time you make a transaction. Your arguments would all make sense if, and I word this carefully, if they were also stripping online "Solo" mode as well. By retaining the online singleplayer element they're essentially making a singleplayer game but with tethered DRM. If they remove that and forcibly convert Elite Dangerous into a true multiplayer experience, then everything you've said suddenly becomes entirely valid.
Granted, it would also cause a firestorm the likes of which would dwarf this one >.>