The entire rust coreutils package, as installed, is 12 MB https://packages.ubuntu.com/questing/rust-coreutils Which is nearly double the gnu coreutils package but still a complete nothing burger: https://packages.ubuntu.com/questing/gnu-coreutils

I think what's happening here is that they've all been compiled into one binary, and then that one binary hardlinked to a variety of names like /usr/bin/ls. Since they all show as having the same inode and the same size.

The other 1.5G of your 1.5G /usr/bin is unrelated to rust coreutils.