QTR-Quadtone RIP

Sorry if I am not understanding this maybe someone in here can shed
some light.

If I were to purchase the UTBO set for my R1800 the 3 inks would go in
the K, PK and GLOP position. How is this different then just putting 1
ink in the K position? Since the 3 use the same ink what advantage
does that give me over using just one since they are the same color? 

I guess I am not understanding this. I want to convert my r1800, but I
want to be able to get a really nice smooth black and white.  Without
grays in the mix or a diluted version (for lighter blacks) I don't
understand how the UTBO will do a good job of this.

Please help me understand what exactly the UTBO is doing.