C++ doesn't have the borrow checker of Rust. Isn't that what made Rust famous?
(Your literal question is a straw man: no, those aren't different, but Rust offers more.)
(Your literal question is a straw man: no, those aren't different, but Rust offers more.)
Unique ownership prevents leaks and double-free, and borrow checking prevents use-after-free. Borrowing is necessary to temporarily relax the exclusivity of uniquely-owned objects and access their interior. Access to interior of a unique_ptr (and shared_ptr) decays it to a reference or a bare pointer that is not managed by the smart pointer any more, and can be left dangling. Borrow checker eliminates the manual "be careful not to leave dangling pointers" part.