The visuals give you the perception and fixed CB. The perception gives you thick or thin. From there you sweep or pivot into CCB.
According to Stan, the visuals get your vision center in the proper location to perceive a CCB view with two fixed edges. This is how he defines a "fixed" CB -- a fixed center with two fixed edges. The perception is the fixed CCB. From this point you come in and place your bridge-V left or right of this fixed CCB line and the pivot from there to the final CCB.
So what do you different that allows you to get a different fixed CCB perception from two identical CB-OB setups in two different locations on the table, and using identical visuals for each setup?