Curious. It renders fast when I hit it on mobile.

Same here – very fast on mobile Safari.

I suspect there’s something going on where webpagetest has an unrealistically slow CPU render time.

I'm assuming there's something going on between the flash of the heart and the app render that's causing the slowness.

By profiling in Chrome (Performance tab -> refresh) it looks like the animations are causing the issue. Having said that, as a user it feels reasonably fast and it's just the flashing content that's weird.