They're still beholden to Google. Their own repo is a set of patches that disable some features. For now, it's mostly feature flags being turned on/off. What happens when Google starts being more hostile and makes disabling features harder ? Can Brave have the manpower to disable that, forever? What if there's a new rendering engine that's 10 times faster but it's so intertwined with a restrictive API that you can't have one without the other?

Brave, for all their talk, are at Google's mercy.

And no, don't give me "but Chromium isn't just Google anymore": it is 90% Google.