This is true, it is complicated. Metrology is a discipline by itself.To point 'the point where THD begins to go vertical to determine amp power' is not that easy and simple.
That's why so many members are hotly debating right now.
With loose resolution(lower counts of point) we can see significant One red hot inflection point.
But, more and more points we get, we got high resolution continuous curve, not the one extruded point. so defining certain point with meaningful consistency is really hard work.
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32 vs 200 points with various ranges each.
It's complicated.
This is why if you want to compare measurements, they must be done following the same protocol. In this case, spacing between points and starting frequency seem to be a minimum.
So you have two solutions:
1. continue following your own protocol, which you are perfectly entitled to. But then you must accept that comparing your measurements with measurements done with another protocol like the one from Amir has no value, and can even be misleading.
2. use the exact same protocol as Amir. This would allow to compare your measurement with the ones made by Amir. More generally, in my opinion, this would bring a lot more value to ASR. I am sure that @amirm is ready to help you in this direction.