Why has Waymo decided to violate its own safety policy and go back to public shadow driving with passengers after saying that was dangerous and stopping it temporarily? (Having said this the practice never stopped for development).

It is a myth that public shadow driving is a viable method to create AVs. That process can never come close to creating an AV. You cannot drive the one trillion miles or spend over $300B to do so. You also cannot run thousands of accident cases thousands of times each or have any more casualties especially a child or family. The solution is to use proper simulation 99% of the time. (That means current products in this industry come up well short. Especially for complex scenarios.)

Impediments to Creating an Autonomous Vehicle https://www.linkedin.com/pulse/impediments-creating-autonomous-vehicle-michael-dekort/

Systems Engineer, Engineering/Program Management -- DoD/Aerospace/IT - Autonomous Systems Air & Ground, FAA Simulation, UAM, V2X, C4ISR, Cybersecurity