I did a little more reading on the JW Player forums. There are parameters that can be set when the player is embedded into the page. By default it appears that the bufferlength is set to 1 second, which might explain why I don’t see the bar stretch out further into the video.
I also read a rather old thread about this occurring when you don’t set the “duration” parameter of the video, so in other words you’re specifically telling the player how long the video should be. This can allow you to clip off the tail end of the video without having to edit it, but also, (at least at one time) has something to do with the buffer bar being displayed.
Sorry for all the geek talk, its what I do for a living. Cheers.