I read "most earners of masters degrees can expect to enter fields with significantly higher salaries, especially later in their careers" as "people with master

I read "most earners of masters degrees can expect to enter fields with significantly higher salaries, especially later in their careers" as "people with masters degrees make a lot of money, so we should people with a masters of education to also have high earning potential." (That may not be what you said; I'm just saying how I read it to clarify discussion.) I should not have implied that you said it indicated job performance; that was the wrong place for me to challenge your statement (as I read it). Instead, I will say that it's not proper to treat a masters in education as giving the same signal as a masters in other fields.