If uutils is ready, then where exactly is it deployed now? Which niche distros have already made this default? How many kubernetes/docker containers are using it? If there was a compelling use case we'd already be seeing it.
What problem are they solving? Size?, No it's typical Rust binary bloat. Speed? The coreutils commands that are slow are typically due to waiting for the disk. Highly CPU bound commands like Bzip2, xz, those aren't in coreutils. Security? How many CVE's in coreutils would have been mitigated by being written in rust? Maintainability? Then why hamper yourself from the start with stating 100% backwards compatibility with GNU coreutils as the goal instead of a well defined narrower scope?
The only reason this is going into Ubuntu is that the rust trannies/furries/faggots like Hector Martin will pitch a fit if it isn't. Instead of organically writing a new app or command in Rust, that people would want, they have to force themselves into existing projects because C/C++ is now extremely dangerous and must be entirely replaced by rust. Instead of writing a new webserver or office suite in Rust, they have to insist on taking over the linux kernel and now coreutils. You must worship the rust girldick thrust in your face.
Welcome to the brave new future of Linux where each and every binary is now statically linked, forced into a sandbox, and hello_world compiles to a binary multiple megabytes in length.