> The only thing unsafe does is let you have an unbounded lifetime.

No, you're wrong: You can create any lifetime. Proof:

    fn oof<'desired>(x: &u32) -> &'desired u32 {
        let ptr = x as *const u32;
        unsafe { &*ptr }
    }

This will take a reference and return it with any lifetime specified by the caller.

> You don't disable anything.

I said "effectively disable". For example:

fn trust_me_bro<'a>(x: mut u32) -> &'a mut u32 { unsafe { &mut x } }

    fn main() {
        let mut x = 1_u32;
        let reference_a = &mut x;
        let reference_b = trust_me_bro(reference_a);
        *reference_b = 2;  -- Whoops
        println!("reference_a: {reference_a}  reference_b: {reference_b}");
    }

After the call to trust_me_bro, two aliasing, mutable references exist simultaneously. This would usually be prevented by the borrow checker, but the unsafe code has effectively disabled it.