Android makes frequent use of unsafe but in their blog post they claim an unsafe rust line has never caused a memory issue. Because they are such a small and focused selection of the code, full scrutiny can be used for any unsafe lines.
Google has actually audited using cargo-vet every crate that chromiumos and fucshia depend on that have unsafe in it. They also have some additional rules related to cryptographic algorithms. I'm pretty surprised they haven't done the same for rust usage in android. https://github.com/google/rust-crate-audits