I'm not "splitting hairs". I'm stating what the MVA site says and what they use each document for. The MVA uses the SS card to verify that the person is authorized to work in the U.S. which is a federal Real ID requirement.You're just splitting hairs. Every piece of document you use is to prove who you are. Proving Social Security is again a reaffirmation that you are who you say you are, even if they call it something else.
If a person shows a SS card but fails to show any of the documents listed under Step One (proof of age and identity), they will not be issued a Real ID compliant license.