I agree that is how the stock '54 switch (and later until at least '59) is Mike. The switch in the schematic the OP posted must play an additional function to provide the single indicator lamp on the dash while using a 2 prong flasher.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12
'52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
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