Lazy load not working for header html tag?

Hi,

Is the lazy load not supposed to work on the html header tag with a background-image?
Here is an example: https://prntscr.com/myrjoe

I added the rocket-loader-bg class and the data-bg attribute as instructed, is anything wrong?

Here is the link to the page with the issue: https://goo.gl/iQnKfb