Same with DE Maverick.

Tecnically, the reciever can be designed either way. There's more to the circuit than just the LED. In the case of being in a switch matrix, the output receiver opto circuit is normally open ( example from DE Maverick below)

opto_(resized).JPG

You can also have both types on the same game, as to what state of the switch is referenced by the diagnostic software to be considered a "normal" state. For example, a ball trough opto detecting the presence of a ball in the trough at game start is going to call this state "normally closed", where a vacant switch elsewhere may be considered "normally open".

We've probably dug this part of the topic into the ground, regardless. The OP is keeping his prehistoric leaf switches in place