I had a look at the Circus schematic, including the section you pasted here. I’ll have to say, I’m not surprised you are confused. It is a bit odd and confusing. I believe that usually the schematic will show the 110V wiring. But this Circus schematic seems to show the 220V wiring, with lug 9 connected as you pointed out.

Have a look at my post linked here that describes the power section of a Monte Carlo which is a Bally of similar vintage. There you will see that the schematic matches up with the 110V setup, so it’s less confusing.

https://pinside.com/pinball/forum/topic/em-pinball-machine-complete-circuit-description-2-bally-monte-carlo#post-5177482

I know Bally schematics the best, so I’m not sure about other brands. For the Ballys, when looking at the schematic and comparing your specific machine wiring, you have to be aware that there can be differences around the transformer and also everything in the coin door, as different coin acceptor setups can be installed on different machines and the wiring will be different. Most everything else should match up.

The schematics also have random errors that you might find as well. It’s all part of of the fun to sleuth it all out.