Well, okay Shriram said the term "homoiconicity" is fuzzy, but the underlying thing (the language of data and the language of programs being the same representation) is real and worth taking seriously. Citing him to wave away the whole concept is pretty wild misuse of the citation. They are refining the claim, not negating it.

> doesn't gain anything semantically

Syntactic properties create semantic affordances. The reason "code as data" matters isn't that the parentheses look a certain way - it's that the AST is a first-class citizen of the runtime data model. Those are semantic capabilities - they determine what programs can express and compute, especially at the meta level. The syntactic uniformity is the mechanism; the ability to write programs that construct and transform other programs, using the same tools as everything else, is the payoff.

Homoiconicity doesn't make Lisp programs mean something different, but it gives you a more uniform and powerful meta-programming model.