I deeply concur with this statement. I think folks here are conflating a one off test versus keeping your redundancy up to date as apps evolve.

Sure you can. Firewall AWS off from whatever machine does the health checks in the redundancy implementation.

What happens when your health check system fails?

It's true, but you can do load balancing at the DNS level.

And you will get 1/N of requests timing or erroring out, and in the meanwhile paying 2x or 3x the costs. So, it might be worth in some cases but you need to evaluate it very, very well.