It's the "healthy cluster" aspect that makes this scary. Partition errors are expected—that's what Jepsen is testing. However, stale reads during normal operation mean that most Galera deployments behind a round-robin load balancer silently encounter this problem. The classic scenario: we create a user on node A, the next request goes to node B, and the user doesn't exist yet. The solution is wsrep_sync_wait or pinning reads to the writer node, but most setups don't use either of these methods because they assume a healthy cluster equals consistent reads.