Correct, you don't. But, I have done it both ways. Today, without removing the tranny & X-fer case. Lots-o-swear words used!
I think that it makes accessing some of the bolts a lot easier if you just yank the tranny & x-fer case.
Besides, they're going to be all grimey. Why not clean 'em up so it's not such a mess the next time you have to work on it. :wink: