Waymo's software has crossed multiple generations of sensors and vehicles over almost two decades. It does not seem to be tightly coupled to a particular device.
Which means the software can safely assume the vehicle will behave within a relatively narrow operating range.
And maybe the software can be designed to be coupled to a vehicle dynamics model that can be updated.
Overall I feel safer in a Waymo than a rideshare now and I only spent a few days being able to use Waymo...
10 years down the line, they won't have that risk.