^ Well, if you referred to Singer as "Bryan", people might be confused as to who you're talking about. Bryan Fuller? Bryan K. Vaughan? Bryan Cranston? Bryan Adams?
On the other hand, I can't think of another famous "Joss".
Exactly. Same for Nolan. If we were using Chris or Christopher whats to stop someone from going, "wait, boardmember Christopher
is involved in 'x' now".
Cameron....James, James Mangold, James Woods, James Marsden, James Franco etc.
Now while Whedon is equally unique a last name as the others Joss is just that much more unique. Plus it rhymes with Boss!