Right, citizenship, residency, and alienage are not the issue (and are nowadays smokescreens), the issue was the federal nexus by getting income from a nationally chartered corporation. (Interestingly, Railroad Retirement was a parallel program to Social Security, but the one had a clear federal nexus and the other just assumes it and goes unchallenged.)

Each person who is alleged to have income according to an information return received by the IRS is responsible for determining if that is truly income (federal nexus) or not, and correcting the record if needed.