So in TESB when you see the back of Vader’s head when the helmet is being lowered, who was that portraying him? Was that Prowse?
Ngl can’t tell if that’s rhetorical or not. In case it isn’t, Prowse played all of the scene with Vader except the choreographed fight sequences, and took on less roles in ROTJ partly due to an injury and partly due to Lucas filming scenes in secret and behind his back, mostly prominent of which is of course the face reveal, which Prowse had (like with the voice) been promised to play. But again in secret Lucas met Shaw at some party and said hey do you want to be in my movie Star Wars to which Shaw was like ‘sure, what is star wars’. Even after the movie he couldn’t remember being in it and his casting was entirely for the star power.
TLDR: Yeah, Prowse had that head prosthetic on in the ESB scene.