It would be shame for the Chief Justice Roberts of the United States to go down in history as the first Chief Justice to incorrectly swear in a new President of the United States by not using his full and correct name even if he was not born in this country. There is no requirement that a President use his entire legal name. Ronald Reagan did not use his middle name, Wilson, for example. For that matter there is no requirement for the Chief Justice, or any Justice to conduct the swearing. All that is mere tradition. LBJ was sworn in by Federal District Court Judge Sarah T. Hughes. But any President could merely swear and/or sign his oath of office.
The Constitution says:
Before he enter on the Execution of his Office, he shall take the following Oath or Affirmation: — "I do solemnly swear (or affirm) that I will faithfully execute the Office of President of the United States, and will to the best of my Ability, preserve, protect and defend the Constitution of the United States.".
OTOH, I wouldn't want to be standing too close to "The Messiah" (whose?) when he utters those words.
I think you miss the point. If the Chief Justice of the United States does handle the swearing of the new President, does he not the have a legal as well as a moral obligation to validate the authenticity of the oath he is administrating?