It used to be true some years ago that you weren't supposed to cross-rotate radials. There's some folks around here that still adhere to that and will tell you the tale.
However, from a technical standpoint, it is not longer true and hasn't been for a long time. It's generally a good idea for Wrangler's to do a five tire rotation. Your mechanic is either lazy or an idiot.
Here's a thread that covers the gist of it: (http://www.wranglerforum.com/f33/2-c...ire-74710.html