I totally agree and I have always in the past myself NOT liked that setting either. Just saying that I finally have one that actually does sound good in that setting and I am pleasantly surprised. I'm not sure why this one sounds good whereas the others I have had in the past have not. I also agree that if one owns one in which that setting is not usable in that setting, and one can change the rotary settings to include a different setting in its place that is one that will be used, absolutely do that. No sense in having a bass with a mode that will not be used, especially when one can substitute it with a mode that will be used.
My guess is that for the standard two pickup basses, Sheldon has set the tone of the bridge pup based upon how it works in the other settings in combination with the neck pickup. The bridge solo'd setting was just sort of, well we have 4 settings and only 4 possible modes, so just include the bridge solo'd even though it might not be useful to most. BUT, the 3x adds so many more possibilities, that the standard bridge solo'd mode may have become obsolete in view of other available modes made possible by the 3x configuration.
I am still going to have to get me one of those 3x basses eventually, and I think it will be in an ABII or a Z. But that is good ways off into the future now for me.