> Prerendering is only useful for sites where either large amounts of data need to be transmitted, or parsing and rendering is slow.

Agreed. Many of my leads for https://www.prerender.cloud/ end up not using the service after we discover the root cause of slowness was due to an initial, slow, render-blocking XHR request, or in some cases infinite loops that eventually get cut off.

AMP seems to allow sidestepping root cause performance issues by creating a pure version just for Google - it's a growth hack - "don't bother refactoring your app (which would require overcoming organizational inertia), just make a streamlined version for us."