BSD does not use GNU coreutils. Is it really unexpected that the developer of a BSD project might have been unaware at the time of a project attempting to replace it, or simply found it incompatible with the stated requirements-- POSIX compliant base utilities. OpenBSD does not care about compatibility with GNU, for example longopts do not work for many utilities, with exceptions to permissive replacements to historically used GNU utilities (grep example).

It also does not address the concerns of higher build times compared the contemporary C counterparts, which also support far more platforms than Rust.

The use of cargo for example suggests that at least a few uu utilities makes network connections at build time to fetch dependencies!

For example something as simple as chown:

https://github.com/uutils/coreutils/blob/master/src/uu/chown...