From the busybox "about" page:

The utilities in BusyBox generally have fewer options than their full-featured GNU cousins; however, the options that are included provide the expected functionality and behave very much like their GNU counterparts.... BusyBox has been written with size-optimization and limited resources in mind.

Neither of these is true for uutils, which is specifically targeting perfect GNU compatibility. I don't think there is a comparable Rust project for minimized utilities.