As cool as it was, that scene bummed me out. It doesn't make sense for him to be so spry and dynamic in that scene and then so old and stiff fighting Obi-Wan right after that in Episode IV.
Now we can come up with explanations, as Star Wars fans often like to do, but the bottom line is that it doesn't pass the eye test. It's obviously not the same character.
Never mind that they had the Death Star plans hand delivered to the rebel blockade runner in that scene from Rogue One but in Episode IV Vader says that the plans were "intercepted transmissions" and "beamed to the ship".
Here's Vader's dad joke.....