They get their sequential trap example wrong.

You can call async methods without immediately calling await. You can naively await as late as possible. They'll run in parallel, or at least how ever the call was configured.

Well, it depends on the language.

In Javascript, promises are eager and start executing immediately. They return control back to the caller when they need to wait. So in practice, all of your promises are running concurrently as soon as you create them.

In Rust, futures are lazy don't start executing until they are awaited. You have to use various features of your chosen runtime to run multiple futures concurrently (functions like `spawn` or `select`). But that interface isn't standardized and leads to the the ecosystem fragmentation issue discussed in the article. There was an attempt to standardize the interface in the `futures` crate, but none of the major runtimes actually implement the interface.