Exactly, neither Rust's Vec nor Rust's String (which is actually a Vec in disguise) store data within the struct itself, it's always stored in an external allocation. This is intentional, to avoid extra branches on whether the data is inline or not. If you have a lot of small vectors, and using less memory is more important for your use case than avoiding the extra branches, there are alternatives like https://crates.io/crates/smallvec that you can use.
