https://travel.state.gov/content/passports/en/abroad/events-and-records/birth.html
Parents of a child born abroad to a U.S. citizen or citizens should apply for a CRBA and/or a U.S. passport for the child as soon as possible. Failure to promptly document a child who meets the statutory requirements for acquiring U.S. citizenship at birth may cause problems for the parents and the child when attempting to establish the child’s U.S. citizenship and eligibility for the rights and benefits of U.S. citizenship, including entry into the United States. By law, U.S. citizens, including dual nationals, must use a U.S. passport to enter and leave the United States.
So if his mother did apply, albeit late, he did get his passport so it looks as though there were no problems.
. You cannot just assume the validity of the regulation.
My sister was born in Panama during WWII. Although my father was an army officer and mother was an American they had her outside of the Canal Zone. They never “registered” her when they came back to the States. When she went to register to vote we found out she was an illegal alien. It was a mess for my dad to clean up and get her naturalized.
He’s lacking showing his Naturalization Form. N550 !!!