If you lose power mid-write to an HDD, of course you can lose data.
This guy sounds like if he'd self hosted he'd be complaining about an HDD failure. It happens- you need to design around it. Luckily, EBS volumes, snapshots and AZs make all of this pretty straight forward.
In my 15 years of experience as a sysadmin and architect, hard drives are far and above the most frequent hardware casualty of power failures.
The EBS documentation states that there's an expected AFR of 1 to 2 per thousand volumes, so you should plan accordingly. Replicate any data that will cause harm to your business if lost to other sources. Keep backups.
This guy sounds like if he'd self hosted he'd be complaining about an HDD failure. It happens- you need to design around it. Luckily, EBS volumes, snapshots and AZs make all of this pretty straight forward.