Obstructing traffic is also against the law.

Something I had pounded into me when I drove too slowly and cautiously during my first driving test, and failed.

Those Waymos weren't moving which is a pretty egregious example of obstructing traffic.

An old rule of thumb is every time a service expands by an order of magnitude there are new problems to solve. I suspect and hope this is just Waymo getting to one of those points with new problems to solve, and they will find a way to more graciously handle this in the future.