The data related to (unlimited) Able bodied seamen qualifications supplied by the USCG and a maritime training facility seem to disagree with your grasp of the facts... There are restricted ratings for lessor qualification and experience but they do not work in the deep sea industry for lack of qualification. Seafarers with lessor qualifications are not commercially valued or sought after by employers...
http://www.seaschool.com/course_details.php?cid=ab
http://www.dco.uscg.mil/Portals/9/NMC/pdfs/checklists/mcp_fm_nmc5_53_web.pdf
https://sealiftcommand.com/now-hiring/deck/