There may be some platform-specific dependencies, but at least when building on Windows, I saw 67 dependencies downloaded.
One thing that may be skewing the count is that internally coreutils is packaged with one crate per command. There are about 100 commands, so you'll have seen at least that many separate crates building. They're listed here: https://github.com/uutils/coreutils/blob/6e8c901204934029c88...
My impression is that ecosystems where tracking dependencies is hard tend to discourage them, while ecosystems where tracking dependencies is easy encourage them. The coreutils crate depends on separate md5, sha1, sha2, and sha3 crates, if managing external dependencies was hard I imagine those would be bundled together. But it is easy, so it makes sense to organise the crates so that each just provides one specific piece of functionality. Think single responsibility principle applied to packaging.