They used to do that (so that everyone picking 1a wouldn’t actually route traffic to the same az), but at some point they made it so all new accounts had the same AZ labels to stop confusing people.

The services that fail on AWS’ side are usually multi zone failures anyway, so maybe it wouldn’t help.

I’ve often wondered why they don’t make a secret region just for themselves to isolate the control plane but maybe they think dogfooding us-east-1 is important (it probably wouldn’t help much anyway, a meteor could just as easily strike us-secret-1).