Earlier quoted context omitted.
Google already can do this by preloading a cached page from its own domain. So this specification is unnecessary. I think the real reason is that Google wants to build a walled garden, but doesn't want the walls to be noticeable. Even with AMP, they display a header that looks like a browser's address bar [1] Also, on that page Google admits that it uses AMP Viewer to collect information about users: > Data collectio…
> Google already can do this by preloading a cached page from its own domain. That's what AMP already did. This spec is better because it ensures publishers retain control over their own content, and doesn't confuse users by showing "www.google.com" in the URL bar for content that didn't originate from Google.
What confuses users is Google displaying a fake address bar [1] or browser displaying the wrong URL.
[1] https://developers.google.com/search/docs/guides/images/amp0...