Where do the salary after attending numbers come from if the school isn't reporting them? Who is surveying graduates 10 years out?
It is not a survey; it is from SSN-linked tax records for students who received federal aid. According to the College Scorecard documentation (scroll down and expand "Earnings"):
To measure the labor market outcomes of individuals attending institutions of higher education, data on cohorts of federally aided students were linked with earnings data from de-identified tax records and reported back at the aggregate, institutional level.