I have located a credible resource, and it seems that my initial perception was correct. Each of the four rear preloads do equate to different damping ranges, though they certainly do seem to overlap.
Sorry, I am not at liberty to reveal from whence this information comes.
Have a gander at this...
[img=[URL="https://i916.photobucket.com/albums/ad4/FJWinNH/2014%20FJR1300%20ES/2014ESSuspensionAdjustment.jpg%5D"]https://i916.photobucket.com/albums/ad4/FJWinNH/2014%20FJR1300%20ES/2014ESSuspensionAdjustment.jpg][/URL]
After several hundred tests of different settings on different preload settings, I think that chart is pure marketing hype....which is a nice way of saying its crap. The damping adjustment range for any given preload setting is very narrow and while there may be some overlap between the two solo settings and the two 2-up settings, there doesn't seem to be any overlap between solo with luggage and 2-up.
I find the STD-0 on the solo preload gives the most plush ride but I cannot seem to duplicate that setting anywhere on the solo plus luggage preload setting. Likewise, the STD-0 setting on the solo plus luggage preload cannot be duplicated anywhere on the 2-up preload setting. All seat of the pants impressions of course but I can't see any reason to have settings with as much overlap as the chart suggests.
I'm also very skeptical that the fork damping settings change at all except for the base preload settings. If they do, I sure can't feel it but it does seem possible that one could fine turn the fork damping by raising the motor position in the fork cap....which really doesn't seem necessary since the fork damping always feels right.