I've been thinking a lot about this, and this is why I think designers are toping the chart.
Design as a practice is uniquely difficult to quantify, and design work in it of itself is even harder to verify.
Take code for example, it either works or it doesn't, it compiles or it breaks. But design exists in the ambiguous gray area of taste and subjective judgment.
Designers get tons of highly subjective feedback, "make it pop," "it feels bland", "it’s missing something, I can't quite name" , yet they're expected to deliver systematically, almost programmatically, like developers.
But creativity isn't a faucet that can be turned on and off at will. Yet, designers are expected to consistently output high-quality, creative work quickly.
I think for a design to be great, there has to be an emotional investment into the project. You have to care deeply, because you know you are not just drawing rectangles, you are trying to build a meaningful experience.
Now put all that weigh, pressure and uncertainty together and you get this chart with design and other highly ambiguous, creative roles like research and growth at the very top.