Generally the Design Manager or Design Director (Murayama) is "responsible" for the design although the ideas come from the designers under him or her. What you hear about the whole team being vital is very true. But sometimes a design is so striking and original and one designer's (Cox) vision so pure and undeniable that they get the credit alongside their superiour. I've never heard anything about Simon doing the interiour until today. So yes, exteriour. Do you have any source for your information or anything?