Hi Barber,
FWIW:
1. This type of engine start, was explained to me over 50 years ago by my Dad, (born 1902), who was a mechanic in the 1920's & familiar with Model T's, A's, & any gasoline engine with "manual" spark advance.
2. This type of engine starting by turning the switch "ON" and moving the manual spark advance up & down can happen "only" first while having a proper air/fuel mixture in one of the engine's combustion chambers; & secondly, while having the distributor cam & rotor positioned such that the ignition points can open & close to generate a hot spark from the coil one of the spark (4) spark plugs.
3. For example, if a Model T or A engine is cold & has been inoperable for a spell, & if a fuel/air mixture was initially present in a combustion chamber after turning the ignition switch to "OFF", after time, the composition of the air/fuel mixture changes to where the engine "cannot" start.
4. However, if one cranks the engine with or without the choke & provides fuel in the combustion chamber; or if one shuts off the engine whereby in either case there remains a proper unburned air/fuel mixture in one or more of the combustion chambers, the engine can start if one moves the manual spark lever up & down which causes the points to open & close thereby sending a spark to one of the spark plugs.
5. This type of start is rare with a Model A; but it can happen far more often with Model T's because the Model T has four (4) ignition coils, one for each cylinder & combustion chamber. I started our local Ford Dealer's owner's Model T like this over 50 years ago by turning the switch "ON" & moving the T spark lever up & down -- he never knew his Model T could start like this when his engine was still warm.
6. We may forget that todays modern cars safely start only in "PARK"; however, a "CARDINAL VINTAGE CAR SAFETY RULE" is to always get in the habit to "ALWAYS" start in "NEUTRAL" to avoid accidents & possible death of a love one.