I'm not sure articles like this one do non-database professionals any favors by associating unrelated concepts that are often found together such as relational databases and ACID compliance. There are both relational databases that are not ACID-compliant such as MySQL with the ISAM storage engine and non-relational databases that are ACID-compliant such as Spanner, FoundationDB, etc. The data model doesn't imply one or the other at all.