If you look at the front park,turn lamp, it shows 2 wires but has 3 places for connection. 1 is blank. Furthermore, if you look at all the exterior lighting diagrams, you will see the blank spot is now hooked to a brown wire and where the light blue or dark blue wire was, is now a blank spot in the diagram.
Same for the rear park, turn lamps, they are only showing 1 circuit at a time. You will have to go to another part of the exterior lighting diagrams to find the other part of the circuit.
I don't know why GM did the diagram that way, but it can be confusing. Rest assured that park, turn lamps do indeed have 3 wires to them.