When I did a rough edit of ROTJ years ago that did this restructure, I had Luke say to Yoda, “Why didn’t you tell me?” The idea being that Yoda confirmed the fact offscreen sometime between the films, but now before Yoda dies, Luke is wanting to understand why he chose not to tell him.

I could see an edit skipping that by having Yoda say something like, “Unfortunate it is, that Vader told you.” It kinda of implies they’ve already talked about it, and Yoda is just lamenting how this complicates their final confrontation.

I also can see how one might wonder why Obi-Wan hasn’t appeared to Luke yet if he’s been on Dagobah all that time, but we know Obi-Wan can commune with Luke on different planets and in space, so I think that question is there either way you cut it.