The main improvement Rust provides is memory safety. It's very easy to make mistakes in C where you could overrun a buffer or something, introducing unexpected crashing and making it vulnerable to exploitation by malware or whatever. Rust eliminates a whole category of issues with their clever memory management paradigm. The improvements in this schedule probably have more to do with the strategy used than code efficiency.

Linux has quite a few schedulers. The performance of this new one is almost certainly a result of different algorithms used, not an effect of refactoring the existing ones, nor the language it's written in.

I don't think I'll dig in to the code just now, but if it turns out to have much practical value, perhaps we'll eventually see an article about the design.