The biggest wrapper that gives guarantees is the standard library, and usually, when people say that Rust does not do something, they have standard library in mind. For example, standard library made the choice to hide panics in out-of-memory situations. That does not mean you can't write your own version of relevant structures to gain different guarantees. I like to highlight the actual strengths of Rust (as a tool) instead of particular implementation details, especially when we are talking about situation (kernel) where Rust is used without its standard library.