[jdmichal]

If someone is using a SSN as proof of citizenship, they are blatantly wrong. SSNs can and are issued to aliens.

https://www.ssa.gov/pubs/EN-05-10096.pdf

USCIS lists as common proofs of citizenship: US birth certificate, US passport, certificate of citizenship, or naturalization certificate.

https://www.uscis.gov/sites/default/files/USCIS/Resources/A4...

[maxerickson]

I imagine they are thinking of it being a list C document:

https://www.uscis.gov/i-9-central/acceptable-documents

(an unrestricted SSN is proof of eligibility to work in the US)

[this-dang-guy]

Yes, and no less than 3 of my former jobs required a photocopy of the card itself. You can argue legal requirements, or you can shut up and be paid.

Sometimes it's better to be paid than right. (Especially on your first few jobs)