This is an absolutely brilliant example of montage (in the original sense of the term).
Heaps of the comments are praising Guinness’ acting for how he subtly says things about the true relationship between Anakin/Vader and himself. But of course, not even Lucas knew that relationship at the time, let alone Alec Guinness. And yet, those comments are so incredibly right. It’s shown throughout, but I think the reaction shot when we go back to Guinness at 2:14, after “and a good friend” -> shots first of Anakin, then of Vader on Mustafar. In context, how could you possibly not read it as him reminiscing with regret, even if the original intent was just remembering he had something else to show.
It’s really just a masterful demonstration, and brilliantly edited.
Stamets