I don't understand the original article as stating that all data maps well onto an RDBMS, but rather than if you are using an RDBMS, you should use SQL rather t

I don't understand the original article as stating that all data maps well onto an RDBMS, but rather than if you are using an RDBMS, you should use SQL rather than adding additional layers. If you want to use a non-RDBMS, then by all means, SQL won't be a good fit. I use Amazon's DynamoDB all day, every day, and I wouldn't dream of using SQL there.