They can actually be private. What if you set up a proxy or a VPN with the express purpose of masking your real IP address, and then WebRTC barfs it out on demand anyway?
Again, WebRTC does not "barf" out your real IP in a VPN situation -- it barfs out the VPN's internal IP, which is meaningless to anyone except for the VPN's operator (and they have that data anyway).
Your actual, ISP-assigned IP remains hidden to any site you visit.
I thought it would provide every IP address held by the system, which would include both the internal VPN IP address and your actual ISP-provided IP address.
Your actual, ISP-assigned IP remains hidden to any site you visit.