I am the WebCall developer. I can see a number of people are using the service right now. However, I can not see what is happening on the P2P links. If you run into issues, please let me know. Same if you think there is anything missing.
But there are many other aspects. Whenever you call someone on their phone, you interrupt that person in the middle of something. When you set up a call with Duo, you give the person a bit of lead time. I love this.
In the future, telephony will be much better than what it is today. And it won't be video.
Summary is people like the speaker more and perceive them as more intelligent with high quality audio.