Nah. Part of the narrative was that various Availability Zones (AZ) in a single region would be on "different flood plains", and be attached to different power

Nah. Part of the narrative was that various Availability Zones (AZ) in a single region would be on "different flood plains", and be attached to different power grids. The essence of this design is that a single event, affecting either the ground (floods) or electricity (a grid), would not be able to single-handedly kill all AZs in an AWS region. Source: I used to share this stuff a lot, in public, representing AWS.