“the high-level takeaway is that Mozilla’s version of Manifest V3 keeps the feature Google removed, while adding support for the more limited replacement as well.”
Firefox 109 ships Manifest V3 and keeps the request-blocking API that Google cut from Chrome. Google sold the removal as a security and privacy shift. Mozilla calls content blocking one of the most important uses for extensions and accepts the risk. The browser built by an ad company decided ad-blocking was the security problem.