He was briefly an unpaid intern.
https://studyinthestates.dhs.gov/2015/11/uscis-explains-if-u...
> USCIS is frequently asked whether an unpaid intern needs to complete Form I-9. In general, an unpaid intern does not need to complete Form I-9 unless he or she will receive remuneration, which is something of value such as no-cost or reduced-cost meals, lodging or other benefits in exchange for his or her labor or services.
I can see how someone'd leave that off a green card application for that reason, which is more plausible than hiding an association with a UN agency while applying for a green card during the Biden years. (If anything, work for the UN and a close ally's embassy should increase trust here.)
Given https://www.uscis.gov/sites/default/files/document/forms/i-4... says things like "Have you EVER been a member of, involved in, or in any way associated with any organization, association, fund, foundation, party, club, society, or similar group in the United States or in any other location in the world?" there's a good chance every single green card applicant has forgotten to list something. Do I include my kindergarten? The music club I was in as a toddler? Joining a political party's subreddit? Donating $10 to a charity ten years ago?
Hell, I'm "associated with" Hacker News, but it wouldn't go on my I-485. Should that get me deported to an El Salvadorean slave camp?