Right, bootstrapping needs a rendezvous point -- that's true of any P2P system, including the wg version. The difference is what the rendezvous knows and costs. Here it holds no accounts, no registry, and nothing that grants access, so it's a phonebook rather than a keyring, and it's out of the data path so it's cheap to run and you can self-host it.

On generalizing: wg wins for "put these machines on one network." WebRTC wins on reach, because the connecting side can be a browser -- a phone, a borrowed laptop, a machine you don't administer -- with nothing installed. A wg jumpbox still needs a client on both ends and a public IP for the box. Different tradeoff rather than a strictly better one.