I was finally able to try it out and this is exactly my observation too.

I've got a very similar score of 0.323 for an Angular SPA with a bunch of dependencies (1,276 kB, 44 requests) that basically shows 5 jpeg images.

Would be interesting to see the result when using JPEG instead of PNG. However it's still easy to gamble, just display some large JPEG images in full size and the score will approach 1.

Edit: By the way, here's a working screenshot link for the score above (image size 3,947 kB): http://www.webbloatscore.com/Screenshots/aeea9b6a-4852-4b01-... They screenshot the whole page.