Redis is often a cache, so if your persistent data is lost who cares.
Not exactly the example I would hope for, in fact it seems duplicitous as a choice.
Databases are generally not what k8s is intended for: rapidly scalable stateless servers. There's real concerns with operators I've seen as to all the different conditions (expansions, failover, backups, detailed health checks, persistent disk management, version upgrades, boundary conditions like full disks, and if course encryption headaches).
I am not a k8s expert, I was involved with an attempt to migrate Cassandra to k8s and did not like the operator I saw at the time.
Every db system has very specific nuances in data storage, io optimization, bandwidth for requests and backups, etc. a one size fits all operator project seems like it will invite trouble.