I think the main thing is the point is the adblocker is in there. And as another poster pointed out, they do use the webkit engine, but they can do lots of things besides that to improve the browser from “reskinned safari” like lots of people seem to be claiming.
That's fine, but that is moving the goalposts. GP said that Firefox is so good on Android because it's important to have ad blocking, and Brave meets that need just fine.
..on their search, not the browser. That's like saying Safari has "anti-privacy/adtech builtin" because Google is their default search engine. You just switch to a search engine of your liking.