Are these tensile test results?

I have to say is this - I dislike when people provide data for comparison in graphical format but plot that data on different scales. It makes it impossible to compare without mental gymnastics (recalculating and replotting in your head to understand how they actually compare).

If I did it correctly (in my head), the butted spokes are effectively stiffer (steeper slope) and have higher breaking strength. Is that correct?

Is this from hardening associated with the butting process or do they get annealed? Harder (stiffer) is almost always stronger.

Is breaking strength the key parameter for a spoke, or is it yield or fatigue strength?

Failure mode is also an important characteristic in these tests? Did they all fail in the same way, at the same location?

Absent answers to those, I do not want to draw any conclusions.

I say that because I have broken many, many good quality spokes in my riding - butted spokes, usually not at the head or threads. A typical failure would look like a tensile failure in the thinner section near or right after the transition from the thick to thin section. Was it simple tensile failure (loading) or was it a fatigue failure? New York City roads were notoriously bad.

I have some good quality wheels with good rims and double butted spokes that have lasted me 40 years. They are showing their age but have been a blessing. I've never broken even a single spoke but roads out here are relatively smooth.