Agreed. AWS RDS instance types are just EC2 instance types prefixed with "db." and you're choosing either single-AZ or multi-AZ deployments so presumably AWS is just spinning up 1 to 3 EC2 instances with some preconfigured software on them.
Aurora is a completely different approach where the RDBMS code is modified to directly interface with EBS instead of going through a traditional OS filesystem layer.
https://www.allthingsdistributed.com/files/p1041-verbitski.p...