[5] AMP は独自の「CORS っぽいもの」を使っています。
[2] CORS in AMP - amp.dev, 2022-06-29T13:42:49.000Z https://amp.dev/documentation/guides-and-tutorials/learn/amp-caches-and-cors/amp-cors-requests/?format=websites
For same-origin requests where the Origin header is missing, AMP sets the following custom header:AMP-Same-Origin: true
For same-origin requests where the Origin header is missing, AMP sets the following custom header:
AMP-Same-Origin: true
AMP-Access-Control-Allow-Source-Origin: <source-origin>This header allows the specified source-origin to read the authorization response. The source-origin is the value specified and verified in the "__amp_source_origin" URL parameter (for example, "https://publisher1.com").
AMP-Access-Control-Allow-Source-Origin: <source-origin>
This header allows the specified source-origin to read the authorization response. The source-origin is the value specified and verified in the "__amp_source_origin" URL parameter (for example, "https://publisher1.com").
[3] CORS in AMP for Email とは違っています。