It's only render-blocking if put before the content! You can actually see this if you load up the demo[0] and reload the page. For some reason, I've made the mistake of putting the script-tag for the JS bundle _after_ the main content but _before_ the footer. The footer is also rendered on the server, but you'll see - especially if you throttle your connection - that the main app will appear instantly, but the footer ("Try without javascript :)", etc.) won't appear until the JS has finished loading.
This is why today it's common to put script-tags for external JS at the end of the body-tag.