You're talking about implementation now. The text you quoted said "references' introduction into high level languages", not "references' use in the implementati

You're talking about implementation now. The text you quoted said "references' introduction into high level languages", not "references' use in the implementation of high level languages". The quote was about languages' conceptual models, not their underlying implementation forced by a particular type of CPU that code written in the language happens to be running on. A language can present value semantics while doing structural sharing using references underneath, as Clojure's persistent data types do.