Not tightly coupled in obvious ways, but as I understand it they aren’t putting it on pickup trucks, convertibles, or anything toeing a boat etc. Their vehicles don’t have aftermarket suspension systems dramatically changing handling characteristics, or turned one into a stretched limo etc.

Which means the software can safely assume the vehicle will behave within a relatively narrow operating range.

The new (as of now than a year ago) Waymo cars still had human safety drivers last I saw one (a month or two ago). I also don't see them taking customers. So they do seem to slow roll hardware rollouts.