More importantly, it's updating the system WebKit framework, which is a core framework so even if Safari.app was separate, the system framework update forces th

More importantly, it's updating the system WebKit framework, which is a core framework so even if Safari.app was separate, the system framework update forces the reboot. The Safari Technical Previews include their own complete copy of the WebKit framework and link to that (and Safari.app can be made to load WebKit.framework from elsewhere which is how webkit nightlies and from-source builds of webkit can be used)