I think you're misunderstanding the intent of the post. An unsafe block is absolutely meant to ensure everything is safe outside of that block. However it's up to the unsafe programmer to do that. Using `unsafe` is telling Rust "I'm going to break some rules now but don't worry, I known what I'm doing".

So if the programmer doesn't in fact know what they're doing then they can cause bad things to happen outside the `unsafe` block, as this post shows.