Earliest image I quickly looked up was shot on my Quebec & N.E america trip with the Ultimate Pro-Omni pivot package was in April of 2008. I know I got it before that. Yes, at that time I don't think it was called PG-02 but it has all the same components except that knob to loosen, so one can shoot additional rows. I could've ordered with different clamps I chose the turn knob to lock the camera to Nodal slide. Personally Nodal slide is what makes RRS so great.
K.C There is only one Nodal slide, that is on the top perpendicular bar. One attaches to the circular clamp accesory. The difference is $100 additional for that knob, as I see it, the little knob does the same thing, I think more securely, that's my 2c with my experience for almost 3yrs @ 5months, for sure.
Good luck