There may be less than meets the eye in this study, though admittedly I didn't plow through the whole article with all the measurements and two-decimal-place distinctions. The study focused on stress as measured by a questionnaire and after controlling for multiple (but perhaps not all?) sources of stress other than seating dimensions. Discomfort = stress, for sure, but it's not exactly a 1-1 relationship. But if the student got credit for it, who are we to complain?
For me it's mostly about legroom, since I'm tall with extra-long legs, and not especially wide or broad-shouldered. I'll pay extra for a couple of inches of pitch. I won't complain about a wider seat, but that's less important to me, as long as my seatmate doesn't hog the armrest or spill over. My wife is short and doesn't care about legroom, but she has back and joint issues that make it painful to sit in one position very long, so she wants a wider seat she can move around in. If we could afford first class we'd have the best of both worlds, but premium economy will have to do.