Rust Core team member here. Out of the box, the Rust standard library only provides very basic networking support [1]. If you want to process requests in parallel, then yes you need to spawn an OS thread to process the request. We went with this model because we wanted to have the standard library be portable across all our supported platforms, and there isn't really a great standard for doing portable IO.
Instead, we're layering platform-specific code in external libraries. At the raw C-level bindings, we have libc [2] and winapi [3]. For higher level APIs, we've got Mio [4] which abstracts the system APIs, and now Tokio [5], which uses futures to simplify async operations.
We're just working our way up the stack. All of these are being developed by members of the various Rust teams, so they're as "official" as everything else we're doing.
And it's not right. Rust programs can use epoll directly or through abstractions like mio and tokio.
Thread-per-connection is the simplest way to do concurrent networking in Rust using only libstd, but it's not the way that most Rust programmers would actually use (at least, not for a production server handling a large number of connections).
