Such detailed database of fine grained road geometry gets stale very quickly, due to road maintenance and road construction. In US highway lanes are shifted sideways frequently.

You underestimate how frequently details like this change in the real world and how difficult it is to reliably integrate them into the mapping models with very low error rates.

Aggregating this data in something close to real-time, verifying and corroborating that the change to the road model is real and correct, and then pushing those model updates to every vehicle that may need it almost immediately is not really a solved problem.

That seems a very risky assumption for any car (self driving or human driver) during flash floods. "Turn around don't drown":

You think you know how deep it is under because you've taken that road many times before (or in your case you have historical laser measurement)

But you don't know:

- Maybe the road under fully collapsed

- Maybe the flow of water is extremely strong, so you need to accurately estimate that too.

That's so much extra complexity

If they have a pre-existing database of every road, sure. And if it's kept up-to-date at all times in all vehicles.