I too fixed performance problems in that repo a few years back and did a write up on it - https://jackson.dev/post/rust-coreutils-dd/
I'm glad this project is getting some more attention, maybe even getting funding from Ubuntu since they're using it? Last time I touched it most of the code was still pretty clearly written by Rust beginners and non-systems programmers so it likely had/has many such issues to uncover. Ubuntu putting it into their distro should hopefully get more experienced (and actually paid!) devs taking a closer look.
It looks like that tool is more or less built by a single developer (you already trust their judgment anyways!), and even though the code came through in a single PR it was a merge from a branch that had 79 separate commits: https://github.com/binwiederhier/ntfy/pull/1619
Also glancing through it a bit, huge portions of that are straightforward refactors or even just formatting changes caused by adding a new backend option.
I'm not going to say it's fine, but they didn't just throw Claude at a problem and let it rewrite 25k lines of code unnecessarily.