Of course SC 38 was used. The fight is actually good and actually fits the characters personalities and skill sets instead of looking like two old men fighting with sticks (Vader is 42 not an old man and is supposed to be an expert duelist who “Helped the empire hunt down and destroy the Jedi Knights”). To me that’s enough to forgive it being different.
Besides, of course the fight scene is going to be filmed differently then the talking scenes.