That's still not really what I'm looking for. I am curious about a “what we keep, for how long” policy for the sensors on the outside of the cars like the Flock one I linked above.

Your second link does mention cameras and microphones outside the car but doesn't mention what they keep (full video? stills? LIDAR? RADAR?) or for how long:

“Waymo’s cameras also see the world in context, as a human would, but with a 360° field of view. Our high-resolution vision system can help us detect important things in the world around us like traffic lights and construction zones. Our systems are not designed to use this data to identify individual people.”

The “Our view on your privacy” section links to the same page as your first link, and that page's “What we keep” section is explicitly only about riders:

“We will retain information we associate with your Waymo account, such as name, email and trip history, while your account remains active.”

Right. I merely shared the closest thing that I could find, and as mentioned, the first link is specific to the ride-hailing service. Notably, in the second link, there is a reference to sharing information with law enforcement, but it's generally lacking in details.