"All of the Clojure collections...are efficient and inherently thread-safe."

https://clojure.org/reference/data_structures#Collections

"Seqs differ from iterators in that they are persistent and immutable, not stateful cursors into a collection. As such, they are useful for much more than foreach - functions can consume and produce seqs, they are thread safe, they can share structure etc."

https://clojure.org/reference/sequences

I think it's a fundamental enough property of clojure data structures that it would be redundant to mention it in every docstring.