Waymo seems to be unnecessarily secretive about this. Why not let reporters visit the control centers? Zoox had the New York Times visit one a few years ago. It came out that there are about 1.5 support people per car. Nobody has a steering wheel. They hint to the cars by dropping "breadcrumbs" on screen.
The ratio of workers to cars matters more, imo, than whether the workers drive the cars. The fundamental sell of self-driving is that it saves labor. If it effectively doesn't, self-driving essentially going to a luxury rather than a replacement for the existing models.
Waymo has had blog posts detailing this stuff.