I think what would matter from this kind of measure is whether a project's use of unsafe actually has undefined behavior. Like the number of unsafe blocks is not really my concern as much as what the unsafe blocks are doing. If you build a single faulty abstraction via unsafe, anything that uses it is broken.

In my projects, it usually comes down to a scenario like needing to write inline assembly or invoke a foreign function, where there are close to zero guarantees the language can give me.