1. Companies like Twilio largely created the explosion in spam calls by providing extremely cheap, programmable calls, so I'm always a little skeptical when the company selling the poison is also selling the antidote. 2. I really don't like the idea of a single company being responsible for a global verification system for something like phone calls. How are decisions made over what is verified (e.g. the example shows "call purpose" snippets on the screen - if I put something there saying "I have an important flight update", but then my call is "You're only getting free peanuts on your flight, but if you enroll in this MileagePlus card you'll get snack mix too!" who judges that?)
Overall I'd just say with all the consolidation of power with US tech giants I am extremely wary of giving them anything else that could consolidate that power further. I would much prefer an open, federated model.