Tim, back in the days before computers... we installed a lot of ei/s with dwell extenders with factory coils. The fact of the matter is... the cars started quicker, with less cranking and idled with higher rpms in almost all cases. Did the engine get modified to make more hp???? NO.. Did the engine make it combustion process more complete so it could make its rated hp... YES...
Heathkit in particular had a bypass switch on it that would cut the ei ... IN or OUT of the circuit. And yes.. .by operating the switch, the rpms would increase or decrease a bit.... Problem with the Heathkit units is the multivibrator transistors would not work in cold weather, or at least some of them, so we would have to put the unit in bypass mode till we could order extra transistors and find some that would work correctly below 30 degrees... So again, with no computer, only carburetors, factory coil, the ei units would make it idle faster, and make it crank less to start as could verified and shown... Later we took the toyota ei modules and moved them to carburetor cars. But as no bypass switch, it was harder to prove, as you had to check the idle speed before and after installation, to see the difference.
Your argument is that a "correct unit" will start well. Problem is.... That as the battery ages, there is more and more of a voltage drop while cranking. NO one changes their batteries weekly. A ei unit will correctly keep the voltage to the coil and more importantly the current flow to the coil high, even during cranking, And this is what makes them work and start quicker and idle higher.
After emissions and computers came along, the newer high voltage ignitions, timing management, and excellent fuel control fixed these problems. But as the older systems were subject to starter wear, battery wear, battery cable resistance, wire corrosion, points resistance, plug fouling and performance, a ei system would overcome, or improve these problems. More hp,, NO, but always at max hp obtainable even years down the road. Remember, most ei systems extend dwell or ... to put a different way, they fully charge the coil for each firing cycle. Back in the day, a dual points system with stagger settings on the points was the only other way to accomplish this. The first set of of points was rotated so that it close early after the fire cycle to start charging the coil sooner, the second set would open later and be the fire signal for the coils field to collapse and trigger the correct timing for the fire pulse... ie it extended the dwell.... secondly it lowered the resistance as well.
I really never went to a high voltage coil in those days as we had more problems with valve spring floating as our limit on rpms. yes, we increase valve spring pressure, pulled studs out of head, then pinned the studs and experience higher cam wear.. the etc etc etc... It was all a matter or money... as the final limit...
But for the average guy, an ei can be useful, particularly if he is not a mechanic or have a points file handy with a booster box, everytime he starts his tractor. For some of us, popping a cap and running a dollar bill through is a no brainer, for others its rocket science.