Cassandra has monotonic reads so it is strongly consistent as long as you have a quorum of nodes. I haven't yet read the link you posted but it's coming from a vendor that is aiming to replace Cassandra so I'll take it a pinch of salt.
Dynamo sucks. BigTable IS strongly consistent. https://ai.google/research/pubs/pub41344 F1 DB from google. Facebook uses MySQL. DynamoDB IS built on top of Mysql/Innodb.
