The problem is more that Rust is going to be automatic in your security more often, while C++ would require more thorough review.
But the code in this article is micro-optimized, and overlooks the common trend of micro-optimization in C++ often leading you into the twilight zone of unexpected undocumented behavior and "luck" when getting desired results rather than granularity well defined syntax. You basically compare the two with artful precision which means you do not get to notice the very common trend of what is safe Rust is often unsafe C++ in the default design.
No, the entire point of Rust's "fearless concurrency" is guaranteed data race freedom by the compiler, something C++ doesn't even try to enforce. Modern C++ can still easily have data races.
The problem is more that Rust is going to be automatic in your security more often, while C++ would require more thorough review.
But the code in this article is micro-optimized, and overlooks the common trend of micro-optimization in C++ often leading you into the twilight zone of unexpected undocumented behavior and "luck" when getting desired results rather than granularity well defined syntax. You basically compare the two with artful precision which means you do not get to notice the very common trend of what is safe Rust is often unsafe C++ in the default design.