There were also a method cutting the ignition for every other or every third cylinder in a changing firing order which lead into "50%" and "33%" settings between all out and idle. Check the first youtube-link I posted.
If you kept cutting the ignition of every other or third cylinder you'ld end up with fouled up spark plugs in short order on those cylinders. The Gnome Monosaupapes actually had an elaborate gear works on the magneto control that rotated the "off" cylinder plugs alternately with the ones that were receiving ignition sparks, so to keep all the plugs relatively clean and hot. The other thing about the early Gnomes were that the intake valves were in the head of the piston, were complex and needed servicing every 50 hours of operation. Since they were operated by atmospheric pressure they limited the altitude ceiling and the power output.
The Clergets, Lehones,and Bentleys had individual air and fuel controls, some were in a semi automatic linking arrangement, but most could be individually adjusted. You didn't reduce the throttle much below 50% so as to keep the flow of Castor oil well distributed in the engine. The oil was pumped crudely into the intake runner and since Castor oil doesn't mix well with gasoline, it was drawn along by the fuel-air mixture.