Yes, that's correct. Whenever you write something in Rust, the license is automatically permissive. In fact, both US and EU copyright law automatically grant an irrevocable, perpetual license to use any and all Rust code that has ever been written for any purpose at all, including for commercial purpose, unless the code was written by a corporation.
Or, you know, you could just:
[package]
license = "GPL-3.0-only"