One detail which I feel must be mentioned: if you block `ampproject.org` by default -- directly or by blocking 3rd-party javascript by default, -- you will be "punished" with a 8-second delay before the page becomes visible.

This is an entirely artificial delay, implemented through an inlined style CSS animation in AMP-based pages:

    animation:-amp-start 8s steps(1,end) 0s 1 normal both}
    @keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}

I can't see any good reason for such delay. If you are not aware of this 8s delay, you might be misled into thinking the page is broken and that `ampproject.org` is really needed, while the page renders just fine without it, except for the delay.

Example: https://ampbyexample.com/