Browser extensions are becoming a notable security vulnerability, with many high profile extensions falling into the hands of (or being sold to!) bad actors. The arbitrary code execution method of ad blocking (e.g. uBlock) is very flexible but it means that without ongoing comprehensive code review using one puts you at risk if the extension ever changes hands or has a backdoor added.

Apple's method avoids this issue by never letting the extension see the page contents, it only provides match lists of what to block that the browser then enforces. Even if the extension became malicious it has no access to private data on the webpages it is ad blocking on.