I don’t care which is more accurate, but eyebrows convey so much emotion. People without them look pretty alien, so having the redeemed Vader in his only real scene with them heightens the emotions Shaw gives off.
Being “pro-eyebrows” myself 😛 I also had never even thought of this aspect since when talking about it you generally have a static image in your mind as posted above. It always pays to remind yourself in such discussions that you’re talking about a motion picture which some elements present or missing can have a large impact due to their effect in a dynamic story telling medium.