Interesting! I didn't know that either. Probably because I only sort by Collections. But still. I think I'll have to check out this mysterious users guide.
Joking aside, I think the reason I haven't looked at it is because most of the user guides I see tend to be rather lame. Older Kindles' guides never had anything in them that I didn't learn myself just from messing with it a little while. I guess I just stopped reading them because I assumed they were all the same.