Looking at the picture that you show in your link above, I wouldn't be able to comment on the reason why he did it personally.
Hey might have made himself a set of shock-hoops, or needed to lower his shock-mounts, or .. any one of a dozen reasons.
Generally, I would go with what K&L suggested .. it was done by race cars owners for a different shock feel ..
And Shawn .. take your shocks off, flex your beast till it can't go anymore, then measure your compressed side and your extended side. Use those measurements to contact Rancho (or any shock manufacturer you desire) through their webpage and just order it. There is always the ability to check with your local 4x4 shop as well, as they normally carry a wide range of shock sizes for just about every lift kit on the market.