It goes, makes the machine think it has a hopper by grounding the coin output signal.
With no coin passing through the hopper optic the IR transmitter LED in the optic is sending IR to the receiver transistor turning it on and grounding the coin out signal.
A coin through the optic blocks the IR signal and the coin out signal goes high for the amount of time it takes the coin to pass.
Jumpering pin 6 to 9 on the machine side hopper "S" plug (after removing the hopper) does the same thing as the jumper on the backplane board.