The behavior you describe occurs if the useragent blocks the URL https://cdn.ampproject.org/v0.js which does not have anything to do with ads or analytics.
Certainly an ad blocker can be used to block any URL, but I don't know of any that block this one by default. If there are any, let me know and I'm happy to file issues to get that fixed!
If a user chooses to block this particular resource which the page needs to load, then the page still loads after 8s.
Similarly, if the site owner chooses, they can run the AMP Toolbox optimizer (https://www.npmjs.com/package/@ampproject/toolbox-optimizer) which lays out the page server-side and removes this CSS flash for most documents. Some documents can't be laid out until the viewport size is known.
Certainly an ad blocker can be used to block any URL, but I don't know of any that block this one by default. If there are any, let me know and I'm happy to file issues to get that fixed!
If a user chooses to block this particular resource which the page needs to load, then the page still loads after 8s.
Similarly, if the site owner chooses, they can run the AMP Toolbox optimizer (https://www.npmjs.com/package/@ampproject/toolbox-optimizer) which lays out the page server-side and removes this CSS flash for most documents. Some documents can't be laid out until the viewport size is known.