Your impression is not that far off based on what the staff expressed to us. The SAASS selection board looks at an applicant's ROP and ranks accordingly. Based on the initial ranking, the faculty will then review each applicant's writing sample to ensure there are no major red flags present. Assuming that the writing samples and board rankings cohere, the list should mirror the original list. There are some attempts to balance the class based off of AFSC.
People tend to apply for the MDOS elective based off of the assumption that being in the program will help their chances. Realistically, the data do not seem to support that assumption. MDOS does expose one, however, to a small selection, and only superficially, of the works that will be read in SAASS.