unique_ptr is unfortunately still unsafe (in the Rust sense): there's nothing in the language stopping use-after-move of the unique_ptr value itself (which is a null-dereference and undefined behaviour), nor references to the interior becoming dangling.

Owned data in Rust (which is all data by default, unlike C++ which must opt-in via unique_ptr) has stronger guarantees than those provided by unique_ptr. It's still possible to deref a unique_ptr after using std::move.