Except unsafe is used more than just for memory and thread safety. Unsafe can acquire whatever semantics you want it to. It’s just that Rust the standard library and standard language has mandated that memory and thread unsoundness is always unsafe. But I can easily make an additional constraint that I annotate as unsafe and the compiler will help me enforce it (if I recall correctly the embedded guys use this when interacting with hardware even though there’s no memory or thread safety issues & I’ve seen it in other places too). It’s a fairly arbitrary choice about what’s considered safe by default vs unsafe and you can always expand the surface area of unsafe.

As for false sense of safety or not, that’s a value judgement whereas we can actually derive metrics about it (eg. build a version of the compiler that require it be annotated unsafe and then investigate now illegal call sites to count how many errors per instance there turned out to be).