The substance of their business model has always been "we fight advertisers because money should flow to websites through
us". They changed actual terms a few times when called up on their tactics being shady, but that's always been the end goal. In that framework, hijacking referral links is par for the course.
I don't blame them - a man's gotta eat, and they're not doing anything illegal or dangerous - but I've always found very curious that some people actually believe using Brave might be an "ethical" choice. It just isn't, it's simply a better mousetrap.