Clojure has a specification language that can express more and less things than a type system can and runs on mobile web desktop with flexible choices for run times
Good luck untangling re-native built on re-frame built on Reagent built on shadow-cljs built on React native built on React built on Android/iOS when one of those parts change.
You make it sound like more of a tower than it actually is. It's just ClojureScript to React Native. All the others are simple frameworks and build tool to help you scaffold.
Not OP, but I'm guessing they meant it can express more, but it can statically type check less. Since Clojure's system is a runtime contract and not a static type checker.