This vulnerability works by injecting HTML and JS purporting to be from a plaintext version of the site being attacked. In other words, the browser has to accept non-SSL pages from the domain. If your browser just threw away all unencrypted requests for the domain this would never work. Neither would sslstrip or a handful of other tools; the improper handling of SSL certs would have an impact, however.

I could have read that draft wrong but it looks like it depends on headers from the victim site to determine if all traffic should be encrypted. MitM would defeat this.