You are absolutely right. The styling of the car was done by Erickson and Mays. The Chief Engineer's role is to engineer the car.... not to style it.
Thai-Tang's upbringing is an nice heartwarming story and Ford has gotten a lot of mileage out of it but I doubt if it played any role in him getting the job.
What's more relevant is his experience on last major RWD platform (DEW98) and the fact that he was the Vehicle Engineering manager on Mustang during the Bullitt and Mach 1 development.
From what I read, the guy is pretty sharp. Newman-Haas won the Championship when he was there and bombed the next year when he left. He also won an award from the Automotive Hall of Fame. Read this quote from an automotive journalist on the LS media drive:
http://www.theautochannel.com/content/vehicles/new/reviews/2000/afrankl_lincoln.html