I disagree with this statement. Having SSN solves a lot of issues. AOS can take a year or so, and not being able to drive / bank / build evidence of married life is painful. AOS is restrictive as is, it's not worth depriving the new immigrant of vital things. Using passport as ID is a bad idea in my opinion for at least three reasons:
1. Passport is a document for travelling outside of the US. If lost, immigrant will have issues travelling home in case of emergency.
2. Passport has endorsed immigrant visa which is proof of legal entry. If lost and if ever questioned by USCIS, it's hard to prove legal entry without it! No proof of legal entry = no adjustment in most cases.
3. Furthermore, if immigrant only has passport as ID, if lost - they have NO ID and no easy way go get a new ID. State ID / DL is a much better choice to show around. Passport is best kept safe at home when not travelling.
4. Many Americans cannot understand / don't want to / doubt foreign issued documents including passports. It's a much better idea to show state ID / DL for routine identity verification. Don't you want the immigrant to integrate in US society faster?