Yep, two (or more, the spec allows for multiple 103 responses before the "real" response) responses returned from one request.
The one library I threw a test server at didn't respond well. It treated the 103 as the response, and the actual 200 as the body. It was an older library, and the spec suggests using client sniffing to pick which clients to send 103 to. That's kinda when I stopped trying to figure it out, I'm not surprised to learn no one really implements it.