I remember that! A major difference and the reason I believe that happened is the type of spacer...
A spacer should with out a doubt be top quality! That means forged billet aluminum. A spacer that isnt as high of quality is a cast iron spacer, from what I remember (will have to double check) he used a cast iron spacer. These are prone to failing under heavy use like off roading, and if not torqued down properly they can crack.
The billet aluminum spacer isnt like that, they are much stronger and less prone to failure. My brother has been running his for thousands of miles with no issues on his JK. I personally believe if you have a quality spacer its just like running a backspaced rim. Just use billet aluminum and not cast! lol