Maybe not what they meant, but Rust sometimes makes it tempting to just copy things rather than fighting the borrow checker. Whereas in C++ you're free to just pass pointers around and not worry about it until / unless your code crashes or gets exploited.

Speaking authoritatively from my position as an incompetent C++ / Rust dev.

Stable Rust doesn't have a local allocator construct yet, you can only change the global allocator or use a separate crate to provide a local equivalent.