Privacy is not an absolute to be maximized at all costs. Do you have blacked out windows, or do you concede that the practical day-to-day infringement of your privacy is so minuscule and so easily mitigated by window shades that it's not worth the trade-off?
And sometimes you have these curtains open? But what about privacy? Do you agree that sometimes people being able to look into your living room is not a big deal, even if it decreases your privacy by some definition? Great, then you agree that maximizing privacy at all costs isn't your or people's tradeoff point. Same with WebRTC - your internal network's IP is not the kind of privacy most people care about, nor should they.
That said, WebRTC from behind a VPN exposing your personal IP is a bit different. That's kind of like a light you installed rendering your curtains translucent. I'm not sure if it's the curtain's fault, or the light's, but it's certainly not what anyone had expected!
Given that OpenVPN somehow works in a way that doesn't expose your personal IP [1], I'd blame the VPN providers for saying that their VPN anonymizes web traffic when it actually doesn't.
