Literal reading is not serious statutory interpretation
First, one cannot conclude that a subsection has an unambiguous legal meaning merely from a literal or plain reading of the text. All reading is contextual. And all statutory interpretation, even textualism, is an attempt to understand "what they actually meant."
One of the most well-known textualists, Justice Antonin Scalia eschewed hyperliteralism. In the book Reading Law, he quotes from Justice Frankfurter: "Literalness may strangle meaning" (Utah Junk Co. v. Porter, 328 U.S. 39 (1946)). Scalia devotes an entire section to "the false notion that words should be strictly construed":
what is needed is reasonableness, not strictness ... adhering to the fair meaning of the text (the textualist's touchstone) does not limit one to the hyperliteral meaning of each word in the text ... Strict constructionism, as opposed to fair-reading textualism, is not a doctrine to be taken seriously.
The next quote is from the Canadian context, but it expresses the same thing (La Presse v. Quebec, 2023 SCC 22 at para. 23):
the plain meaning of the text is not in itself determinative and must be tested against the other indicators of legislative meaning — context, purpose, and relevant legal norms.
Early in this very term (the October 2023 term), the Supreme Court of the United States released an opinion about the meaning of a list joined by the word "and" (see Pulsifer v. United States, 601 U.S. ___ (2024)). Justice Kagan, for the majority, wrote:
the meaning of Paragraph (f)(1) may become clear if we examine the content of its three subparagraphs — what they say and how they relate to each other — as well as how they fit with other pertinent law. Or stated in the usual language of statutory construction, the answer may lie in considering the paragraph's text in its legal context.
Any argument relying on a purely literal meaning is not conducting serious statutory interpretation. The petitioner does not do this, nor does the government in this case.
The petitioner's arguments are in his brief
If you're wondering what arguments the petitioner presents, you can read his brief, as well as the nine briefs of amici curiae in support of the petitioner.
He presents the issue as such:
Does the [D.C. Circuit's] unprecedented reading of subsection (c)(2)
contravene the statute’s text, history, and legislative
purpose, as well as interpretive canons, and this
Court’s precedent on the construction of federal criminal statutes?
Even from this framing, you can see that the argument is going to pull from all the relevant sources for statutory interpretation. And look at the headings in the table of contents:
Basic principles of statutory interpretation demonstrate that Section 1512(c)(2) applies only to acts that affect the integrity or availability of evidence
- The text and context of Section 1512(c)(2) make clear its focus on evidence spoliation
- Basic canons of construction confirm Section 1512(c)(2)'s role as a residual clause and its focus on evidence impairment
This court's precedent also supports a limited reading of Section 1512(c)(2)
The statutory and legislative history of Section 1512(c)(2) support a narrow reading focusing on investigations and evidence
- The statutory predecessors to Section 1512(c)(2) confirm its narrow scope and function as a residual clause
- The Sarbanes-Oxley amendment did not alter Section 1512(c)(2)'s focus on inquiries or investigations
Beyond the actus rei elements of Section 1512(c)(2), other elements confirm its evidence focus
- The government and the courts have narrowly viewed "proceedings" under Section 1512(c)(2) as involving investigations and evidence
- The mens rea element of "corruptly" in Section 1512(c)(2) does not provide a guardrail to subsection (c)(2)'s "breathtaking" scope
The rule of lenity and the canon of constitutional avoidance resolve any lingering doubt over the breadth of Section 1512(c)(2)
That seems a sufficiently detailed overview to answer your question, but if you want more information, you can read the brief.