No, you can't turn it off with WebRTC IP handling policy. The closest you can get is "Default Public Interface Only: WebRTC should only use the default route used by http. This doesn't expose any local addresses."

Keyword is "should only."

Fact of the matter is I've tested it and it doesn't work on even 50% of scans. In other words, I'm using a VPN and my browser is handing out my local IP address. Unacceptable.

I don't blame Brave for this. They've built it on top of Chrome open source code, and Google Chrome does not even have options for WebRTC configuration. With that being said, if a website utilizing WebRTC is coded correctly, Brave's "defenses" won't stand a chance. The default setting works only for the websites not trying to harvest your WebRTC data in the first place.

tl;dr If you're not behind a VPN, really doesn't matter.