Obi-Wan knowing Anakin took the name Vader doesn’t mean he knew that Vader survived past their fight in episode 3 though, right? The fair assumption would be that the guy you left chopped up and on fire did in fact die from those injuries. Isn’t that the surprising information, and not that Anakin changed his name? I haven’t seen it, but that’s the impression I got.
If you had been set to write an Obi show and had gone back and refreshed yourself on the canon - scenes and dialogue made in both PT and OT - would you have written Obi as unaware?
Exactly. This claim is just a bad attempt to slander the creatives behind this show. In episode 2 Obi-wan hears the name “Lord Vader” and visibly reacts to it. What he didn’t know was that Vader was still alive.
Of course, as always - the fans are to blame. Instead of pointing out a blatant result of incompetency, we should all rally around the writers and help them out with our fan theory gymnastics. Force forbid Disney actually do their own job well to begin with.
In this case it does make sense. Obi Wan was specifically leaving him for dead, and Yoda tells him that he’s Darth Vader, so he knows him by that name. If I remember right, they made a big deal out of the moment he finds out he’s alive in the expanded universe as well, I think in Dark Lord: The Rise of Darth Vader (I haven’t read it.) It makes sense to make it a big dramatic part and for what it’s worth I think it’s one of the things they did well in the show, largely because of Ewan McGregor selling it.
The main issue is whether people in general would be aware that Vader exists or not and whether that knowledge would have reached Obi Wan and friends after 10 years. Apparently not, which would imply he doesn’t go out that often or he just doesn’t leave anyone around to tell stories.