I also thought about the same issue, the term "data" was used a bit sloppily in the article. Similarly the quote from pg explains programming Lisp as manipulati

I also thought about the same issue, the term "data" was used a bit sloppily in the article. Similarly the quote from pg explains programming Lisp as manipulating ASTs, which isn't true in a strict sense, more precise: you manipulate a representation that is much closer to an AST. But I don't think these make the larger points any weaker.