Best argument for Shaw being there is that WE JUST SAW HIM DIE.
The Shaw we saw die and the one who appears as a ghost look very different.
Once again, if you think his ghost should have been scarred, then Obi-Wan’s ghost should be missing his lower half.
It’s clearly the same man.The difference is that Obi-Wan wasn’t cut down until he died. Shaw’s ghost is appearing as someone who never existed.
If the other characters are able to recognize him in spite of his form which they clearly do does it matter if it’s a form he was never in while living??? I don’t think so.
JEDIT: I don’t think most viewers have or had difficulty distiguishing who the third spirit was either so I really don’t get what form his spirit takes form compared to the forms he was while alive really has to do with anything. Not trolling, just being honest.