This is Bug 1845783. It's probably validating on this use case, as the page is a giant frame of another website. Perhaps with language detection if there is no content, we can detect the iframed content.
Bug 1877134 Comment 3 Edit History
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This page is a big iframe, which is Bug 1845783. It's probably validating on this use case, as the page is a giant frame of another website. Perhaps with language detection if there is no content, we can detect the iframed content.