Why clippy-driver command's returns the usage of cargo?

Why clippy-driver command's returns the usage of cargo? Won't it make user confused?

This was introduced in Implement better help for clippy-driver by yaahc · Pull Request #4175 · rust-lang/rust-clippy · GitHub I am not sure what reason there was behind this change. cc @yaahc?

I don't precisely remember if there was a specific reason.