Well they seem to give an A on almost all metric except small images, they claim we could save 50 KB overall LOL. And the reason they are wrong is that retina displays have 2x density per logical pixel.

The suggestion to use a CDN and set up HTTP Caching is a good one. As well as minimizing Javascript. My point was specifically to illustrate how fast an image-heavy page can be without it. It lazyloads images on demand, batches requests and does many other things to speed up rendering.