There appears to be a slight mix-up between "true" streaming and "pseudo" streaming here. I believe true streaming is when video is streamed from a specialist media server over a streaming protocol such as rtsp, rtmp or mms whereby the media is not first downloaded before being available for viewing. I don't think any browser supports this with HTML5 - at least I've yet to see any support for it.
Pseudo streaming appears to be the one that you want, but it is still basically progressive streaming the only difference being is you tell the server at what position or time in the file you want to start streaming from.
Here is an example of HTML5 video using time offsets to move to any part of the video. It should give you all the information you need to try it out for yourself.