All nine justices were able to agree on a bottom-line result in Trump v. Anderson: States cannot disqualify candidates for federal offices from the ballot under Section 3. But they were not in agreement on what the decision should say. I suspect that they were wrangling over the language of the per curiam and other opinions until the last minute as they rushed to issue an opinion in advance of Super Tuesday primary voting (or the Monday release the Court had already announced).
As Mark Joseph Stern noted yesterday on Xitter, the three-justice opinion concurring in the judgment appears to have been originally drafted as an opinion by Justice Sotomayor "concurring in part and dissenting in part." So either Justice Sotomayor was confused about how to style an opinion that reaches the same bottom line judgment of the majority (unlikely), or something changed in one or both opinions. [Sidenote: Who thinks to check metadata by double-clicking random parts of an opinion or searching for ghost text?]
There are other indications things may have been revised quite late. For instance, the three-justice opinion accuses the majority of holding that "a disqualification for insurrection can occur only when Congress enacts a particular kind of legislation pursuant to Section 5 of the Fourteenth Amendment." The majority certainly holds that Section 5 of the Fourteenth Amendment vests in Congress the power to enforce Section 3, but nowhere does it require a "particular kind of legislation." Might this be responding to language in a per curiam draft that was later watered down? It's quite possible the per curiam was changed leaving no time for additional revisions to other opinions.
