When someone builds a skyscraper and then you take one small unit in it and paint the walls a color you like and change the light fixtures, would you say that you built the skyscraper?
Because that’s what Brave (and everyone else who builds on top of Chrome codebase) does.
When the builders then decide to remake the wiring in the whole building so it doesn’t work with your new light fixtures you bend over and take it because you don’t have a choice - you have nowhere near close enough resources to remake the whole wiring for yourself.