It's a little more subtle than that: It's "safe code must be memory safe" and "unsafe code infects the whole module". The stuff you're talking about is "what exact invariants are unsafe code supposed to uphold". Because unsafe Rust is a superset of safe Rust, that being an open question does not mean that what's meant by "Safe Rust" inside of safe Rust is up for questioning.

Work on exactly what unsafe code is expected to do is ongoing.