Late Start Render Time - What is blocking?

[BITS]

I built up a test environment to test some optimization techniques. At the moment I try to find out why the Start Render Time is at about 0,7 seconds in the following example:



Link: http://www.webpagetest.org/result/140806...1/details/

To exclude JavaScript as the source of Render blocking I used the WebPagetest blocking feature.

In my opinion the browser should start rendering the site at about 0,4 seconds because I see no reason to wait another 0,3 seconds till 0,7. Any ideas what can cause the blocking behaviour?