It's a very valid question, and very hard to answer... You need to draw the line somewhere, and say enough is enough, though the later you say that the better.
In onroad it would be somewhat easier to find what works as you can measure average lap times easier and all out power is needed, as dust is less of a problem you could find how the engine wear more easy as well.
For offroad things gets more complicated for sure...
But it's a matter of finding boundaries for every component (so if you aren't willing to blow up engines forget it), categorize and use as many labels as possible, taking notes after notes, measuring what can be measured all the time. Then trying to mix them now knowing how everything works by itself, so you can see if a pattern emerge.
It's easy enough on these small engines, try it on full size engines, it's a nightmare.

After running some commercial fuels I can say that they are all about pushing products fast and easy, some have never done any real hard testing.
And if people would know how sensitive it can become sometimes, people (even top pro's) would blame the fuel far more often then they blame their engines today. They have made an incompatible choice between engine setup, car setup, fuel etc, and just failed to adapt to the situation but in the end blames the engine.