I just had a quick check with TCPView and its test is multi-threaded over https.
HTTPS is more realistic than port 8080 and I presume this means Netflix itself streams over multiple connections to its server. If this is the case, it would help with streaming in its higher resolutions without depending on its CDN being able to deliver the bandwidth over a single TCP connection. I don't have a Netflix subscription to check that out.
What it does mean is that its speed test may not be the speed you'll get on YouTube which streams over a single connection to its CDN, similar to downloading a large file in a web browser.