I like that the article calls then "functional data structures". Every time I call them by their real name (persistent data structures), _at least_ one person will get confused and think I'm talking about serialization to disk.
Is is possible to construct a persistent data structure that is not referentially transparent? I suspect the answer is yes, depending on how you define side effects (example: a persistent array that logs operations). Which would mean "functional" is a more general adjective than "persistent" since it includes both persistence and referential transparency. Wikipedia[1] claims "There also exist persistent data structur…
"Persistent" is but a bullet point on Clojure's own explanation of its data strucures, so I suppose we as a community should follow in the official docs' footsteps :)