The AMP pages on the google search result page cannot be distilled by the Reading List.

This is because the actual page content is in an iframe.
Example page
https://www.google.fr/amp/s/ampbyexample.com/?client=safari

has an iframe to
<iframe class="u2quVpIWVr0__amp-doc" allowfullscreen="true" scrolling="no" src="https://cdn.ampproject.org/v/s/ampbyexample.com/?amp_js_v=6#origin=https%3A%2F%2Fwww.google.fr&amp;exp=a4a%3A0&amp;channelid=0&amp;cid=1&amp;dialog=0&amp;prerenderSize=1&amp;visibilityState=prerender&amp;paddingTop=54&amp;history=1&amp;p2r=0&amp;horizontalScrolling=0&amp;csi=0&amp;storage=1&amp;viewerUrl=https%3A%2F%2Fwww.google.fr%2Famp%2Fs%2Fampbyexample.com%2F" style="height: 116px;"></iframe>

The iFrame prevent to inject the distillation javascript on the page.

A possibility to work around this problem is to open the page directly without the google search container.

The page can be opened directly in https://ampbyexample.com or via the google cache
https://cdn.ampproject.org/c/s/ampbyexample.com/

This cause two issues:
1) detect that we are displaying a google AMP page.
We can check that the host is a google domain and the path starts with /amp/
We may need a stronger test to avoid false positives, particularly as there are a lot of google domains.

2) get the amp address.
A simple way to get the amp cache url is to replace www.google.com/amp by cdn.ampproject.org/c in the URL.
Another possibility is to check the noscript tag in the google page
<noscript> &lt;meta content="0;url=https://cdn.ampproject.org/c/s/ampbyexample.com/" http-equiv="refresh"&gt; </noscript>