It does not.

I find the wild, anti-competitive cross product "synergy" the big tech companies are employing just as concerning as privacy violations.

(E.g. Google search pushing Chrome and other services, Chrome sync logging users into YouTube, Android, Windows pushing One Drive, Apple music not paying the Apple store tax, Facebook harvesting WhatsApp data etc.)

Brave joining those practices leaves an ugly taste.

I asked the same thing to Luke Mulks (VP of Business at Brave) about an year ago when search got out of Beta and he "promised" that the behavior from the built-in ad blocker would be the same as it is any other page. IOW, the ad blocker does not block first-party ads unless you set the browser to "aggressively block ads and trackers".

"can" or "does"? ;)

I guess it does not. How far will they go though? Will uBlock in Brave be able to block the ads?

Yes. Same rules as google. When in aggressive mode, shields will block first party ads. No exceptions.

Maybe, but I would not trust it. Just install uBlock Origin and you're free to completely turn off "Brave Shields" or whatever it is called.