I have no info about the ignition system, but any reduction in warmup time is due to the higher RPM, not more/less plugs firing. Simply put, 3000 RPM will create more heat than 1500, thus the quicker the engine reaches operating temp.
The arguement about oil being too thick to flow well when cold is pretty much obsolete. Modern multi-weight oil starts out at lower viscosity, then thickens as it reaches operating temp.
Modern EFI engines don't need extended warmup periods at idle, a minute or so on the coldest days is plenty, then it can be driven until it reaches full operating temp. It shouldn't be driven hard during the warmup cycle.
The idea of letting an engine warm up before driving was reasonable back in the days of carbs, as the choke restricted air flow, thereby causing an overly rich mixture while trying to drive with it still engaged. EFI overcomes this by not restricting the air flow, but instead it simply injects a bit more fuel to get the richer mixture needed to ignite inside a cold engine.
As for 1/2 the coils shutting off at a certain RPM, it would make sense. Under a harder load, having 2 flame fronts colliding inside the combustion chamber would create the same effect as detonation, which is rather harmful in the long run. 1500 RPM would make sense, since these engines have almost no guts down that low........
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