Short description of your issue:

A4A uses fetchJson to retrieve the public key sets for crypto validation without requireAmpResponseSourceOrigin as an init property. This prevents network level caching across publisher pages.

How do we reproduce the issue?

Enable A4A via exp=a4a:-1

What browsers are affected?

All

Which AMP version is affected?

All

Suggested solution

Recommend either not including __amp_source_origin if requireAmpResponseSourceOrigin is not true or adding new parameter that allows for forceably not including