Well the extended length adds more droop, but that comes at the cost of a longer compressed length as well.
Say you have a 4 inch lift, well you could add 4 inches to your bumpstop and still have factory uptravel, without bottoming out a longer shock. Going back to the small lift, I cant add 4 inches of bumpstop, I would be riding on it going down the road. So the nice thing about the RS55531's is that, I can get this greater extended length, and therefore downtravel, while only extending my bumstops a small amount, retaining most of my uptravel, which means I have a greater amount of total wheel travel.
Or atleast that's how my redneck brain sees it! Hope that helps.