Earlier quoted context omitted.
Except many couples meet in school, where they'd be exposed to a disproportionate number of potential spouses within their own field of study, and maybe to a lesser extent others in related programs within the same college. Which would also be skewed by things like length of study and personality types attracted to particular interests. Eg, Doctors and lawyers often don't want to get married until after school, at wh…
I’ve read that one reason wealth inequality is worse today is because high-education-high-income individuals want to marry other HEHI individuals whereas in the past this wasn’t the case. If the claim about the past is true, it seems to undermine your point
But my point isn't so much that people meet in college, so much as there isn't really a good way to adjust statistical measurements to account for the popularity of a particular field/job, as was suggested up thread.
There are way too many related, interdependent, conflicting variables, with common field of study being a major one, even for the smaller disciplines.