"Firefox Focus continues to operate as a Safari content blocker on iOS, and users will be able to take advantage of Tracking Protection on both Safari and Firefox Focus."
I have not used these APIs but I wonder whether it is faster to use Safari in private mode with Focus as a blocker, or using focus directly. Afaik Safari compiles the blocker rules into some binary representation and is thus able to apply them really fast. Do Webkit applications have access to similar functionality?
Safari will be faster. Focus uses UIWebView, which is markedly slower than WKWebView (UIWebView executes in-process and cannot JIT, WKWebView executes out-of-process and can JIT and is as fast as Safari).
Goes beyond just a browser.