Can someone please explain to me what the deal is with hot starts, what is happening in the above as it pertains to hot starts?
Think about Goldilocks and The Three Bears.
Remember porridge too hot, porridge too cold, porridge just right? The situation is similar when starting an engine with a constant flow fuel injection system. The fuel-air charge presented to each spark plug can be thought of as too rich, too lean, or just right. When it's just right, the engine will start and run easily; mixtures near stoichiometric are easy to light.
All successful starting methods are fundamentally the same. We set up a mixture sweep, forcing the ratio from rich to lean, or from lean to rich.
Either way, it will pass through stoichiometric at some point in the sweep.
Consider the classic lever dance. It's really a sweep moving toward lean from a condition of way too rich. First we flood it (full rich, boost pump on), which ensures we're beginning the sweep on the too-rich end. Then we put the mixture at ICO and the throttle wide open; when we start cranking, no more fuel is added, but we're supplying plenty of air. With each intake stroke the fuel/air ratio presented to the spark plug becomes progressively leaner and leaner. When the ratio passes through the stoich range (or close to it), spark makes fire. We close the throttle and open the fuel (the lever dance), hoping to remain in the sweet spot.
The method is fairly reliable because the flooding process refilled the divider and nozzle lines, which were probably boiled dry after the shutdown. Now when you "catch" the start by moving the mixture to rich, there is actually fuel immediately available at the nozzles. The downside is that it's easy to be ham-handed. Set aside the runaway RPM thing. With the throttle full open, there is a wide range of fuel flow between ICO and full rich. The open throttle makes the mixture knob a gross control.
Consider the "throttle cracked, slowly push mixture toward rich" method. It's a sweep moving toward rich from a condition of way too lean. Leaving the throttle cracked and pulling the mixture for shutdown merely made the mixture too lean to run. So, to make it fire again we just sweep the mixture from too lean back toward rich. Allowing the engine to spin 4~6 blades with the the mixture knob at ICO ensures you really are starting the sweep in the too-lean range; all air, no fuel. Now start forward
slowly on the mixture knob. Since the throttle isn't wide open, mixture knob movement is a finely graduated flow control. With each rev the mixture at the cylinders is getting richer. When each cylinder returns to something near stoich, it will light. Resist the temptation to do anything quickly. Don't shove the red knob; maintain the same nice slow push.
If it doesn't light, you managed to pass through stoich. It's not a problem if you stop and think a moment; you're now at the too-rich end of the scale. You just need to sweep from rich, back toward lean. You want all air, no fuel; do the conventional lever dance if you're comfortable with it.
Or you can do a variation: go to WOT, mixture to ICO, crank, let it hit,
but do nothing with the levers. It will run, more or less, and quit. You just moved everything from the too-rich end of the scale to the too-lean end of the scale by using up all the random fuel in the intake tubes and cylinders. Now you can sweep lean to rich again; set throttle cracked, spin it a bit, and start forward slowly with the mixture.
And what the addition of an electronic magneto does to the mix
It simply widens the "just right" range, as it will light slightly richer or leaner mixtures.
