E.g. FireFighting - It has a lower Workers Comp rating than most construction jobs. In California they often make $100,000 or more and spend most of the time training, cleaning or resting. Most calls are not for fires, but for assistance. There's very little chance of loosing your job and in the unlikely situation where you're hurt or injured, there's a well-funded plan to take care of you.
Compare that with an "Event Coordinator" who's under constant deadlines, paid ~$27K/yr, workes 12-14 hour days and lives in constant fear of loosing their job if everything isn't perfect. No health care and no retirement.
In college one year, I worked 10 hours a week in a semiconductor testing facility. I plugged a chip into the tester, pushed the button, took the part out and penciled the two-letter code returned by the tester. Then I took the next chip, plugged it into the tester, ....
It did pay $13.xy/hr in the 80s, which was why I put up with it.
I could see a big shop having enough work to support a full time drill operator but it is rather like saying you are a hammer operator or a screw driver operator. It isn't complicated enough to need a specialist.
Have you ever tried to center a hole to micron precision? Do you know which drill speed vs feed rate to use for the metal you are drilling? Do you know which drill bit to use? Do you know how to sharpen drill bits correctly? Do you know how to secure work to the table? Do you know how to use a sine bar and gauge blocks to mount your work piece at a precise angle? Do you know how to inspect the surface of the work piece to make sure it doesn't have burrs, specs of dirt etc that could throw the work tolerances out? etc etc
It's not he most in depth job, but it's far from unspecialised.
Looks like they made up some list of things they think should be stressful, gave them arbitrary point values, and scored each occupation.
The authors of the study are CareerCast.com. Not exactly an authority.
No doubt, being a soldier or a firefighter has got to be stressful. But this "study" won't prove it.