What compression ratio is your Skyactiv engine runs on? (sorry, not familiar with these skyactiv engines...for I'm an old-fashioned Mazda guy spending most of my time in their rotary/B series block days)?
My fit came with compression ratio of around 10.5:1, and spec'ed to run on 87 octane gas.
I occasionally run 91 mix (whatever 87I have left in my tank) and the engine feel a bit snappier, but otherwise for the most part: fuel-economy remains pretty much the same as before. It's just that when I turn on the A/C compressor during summer time, running a mix higher than 87 octane rating will reduce the "snap"--drag sensation (when A/C kicks in) and the car accelerates smoother.
Newer fit runs on 11.5:1 compression ratio, and yet still spec'ed to run on 87 octane rating gasoline. Detuned? perhaps so, but so long as it supports bare minimum of 87 octane rating gasoline (R+M/2), that that should be ok.
In your case my perception of skyactiv engine designs has to do with improving mechanical efficiency/reduction of frictions to improve fuel economy. Given all other things being equal (somewhat similar compression ratio to that of most Honda iVTEC engines nowadays, which hovers around 11:1 or more), then it wouldn't be at all, surprised that what you feel about (magic) maybe similar to mine?
Lastly: ignition mapping is not as difficult to understand as many people think:
Remember this: with gasoline engines on OBD-II design now runs on individual over-the-plug top coil configuration (can control individual cylinder ignition timing and mapping), and pretty much all of them comes with a knock sensor on the block as a feedback mechanism back to the ECU, typical engine ignition mapping is designed to dynamically run the ignition timing to just before the 1st sense of "preignition" knock is being sensed. Given the higher octane rating gasoline resists knocks better than 87, and given the ignition timing is dynamically "Read" and actively adjusted, it is of no surprise that by using higher octane gasoline (resists preignition better) the ignition timing will advance a bit further than that of 87, but again, it will stay within the "Safe" zone where the just-before-knocking sound is being picked up by the knock sensor.
Even newer, all computer controlled german diesel engines are like that nowadays, with adjustable diesel pumps and knock sensor to constantly read and adjust the spray timing and duration to minimise that dreaded "clacking" sound and gives better power output and exhaust control.
My understanding...
Q.