Few things to note

1. uutils as a project started back in 2013 as a way to learn Rust, by no means by knowledgeable developers or in a mature language

2. uutils didn't even have a consideration to become a replacement of GNU Coreutils until.... roughly 2021, I think? 2021 is when they started running compliance/compatibility tests, anyway

3. The choice of licensing (made in 2013) effectively forbids them from looking at the original source