It primarily has to make sense to the people that watch the movie. If it doesn’t look like the burnt guy we saw earlier on, if we can’t recognize him, the movie makers have failed at story telling.
Star Wars is not an historical documentary about the GFFA, it’s a fairy tale that is maybe somewhat based on true facts. Like all fairy tales, entertainment is more important than the truth!
If you’re gonna argue that, I found it extremely jarring as a child the first time I saw the pre-SE version of RotJ with some weird old guy in the place of Anakin.