Earlier quoted context omitted.
They are building another monstrosity to be able to masquerade as your entire domain. But it is optional , of course /s
Website authors opting in to letting another server serve content "as" their own domain isn't anything new: it's what CDNs do. The Signed Exchanges standard is actually a huge step up because the website authors get to cryptographically sign their content. With normal CDNs, if the CDN is malicious or gets hacked, the CDN is free to serve modified content on the original domain.
Signed exchanges is considered harmful by Mozilla.[1]
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