Most ad blockers that people use on Android are open source, e.g. uBlock. While due diligence is good, I don't think I've seen any evidence that would suggest gorhill wants to sell my data. You can't compare an ad blocking extension to an entirely different browser (Brave) as a whole. uBlock runs on regular old Firefox for Android.

I appreciate that it would be nice if Google gave us the option to block stuff in Webviews, but it's not a replacement for having a real ad blocker like uBlock that is much more complicated and has many more features. I think the person you are talking to is mainly criticizing Apple for not letting you use such an ad blocker on their OS.