I have to agree with the parent poster, especially given that I have a degree in International Relations but earn a high 'computer science degree' salary since I work in the field. Anecdotally, quite a few coworkers over the years at different positions have also revealed that their degrees are not in the field, but since, like me, they had the skills in it and the experience, they chose to do that kind of work, despite the degree being in a different subject.

I work for a university, and I don't think I have ever heard a faculty or staff member say "All degrees are equally valuable", a google for such only shows 6 results. All with the word not in front. Even doing more liberal searches produces the same results, pretty much every single article says no. Where is the advice you are supposedly getting? Is it coming from an authoratative source? You could really use a citation.

Yeah, sure it is, because that's horrible advice. Does anyone actually believe that all degrees are equally valuable?

I think people have a general idea of which degrees are more valuable than others, a flawed and vague idea to be sure, but it's not obvious that this data is more accurate than that.

I wonder if you couldn't get very similar results by asking people on Mechanical Turk to rank degrees by what they thought was their value.

Regardless of how it fares against other advice, it still has flaws that can significantly affect its accuracy; and I'd want anyone I cared about to understand that before making decisions based on it.