There are no 'unsafe' blocks in Fil-C. I think you trying to conflate 'unsafe blocks' with the fact that there might be compiler errors which might break 'safety'? Which is equally true in any system including Rust.
"Blocks" are relevant as they are how you express programs, algorithms, etc., that you need in order to get something done. Lots of data structures in Rust have a little unsafe somewhere. Users will typically depend on some "specialist" crate author to write them, but it exists, and is a necessary part of practical Rust programming. The pool of unsafety is open and by necessity growing.
In Fil-C, no such specialists are needed, and the pool of unsafety is closed and fixed, no matter what programs, algorithms, data structures you use.
This is not a trivial distinction I think. I think it's easy to acknowledge, especially given its (current) performance cost.