Why does someone want this functionality? Do you expect, say, Oracle to work this way? I honestly don't see this as a useful feature in a database that's operating at scale, but I'm open to hearing reasons for needing this.
FaunaDB (like other highly available databases) is set up to have multiple replicas of the same data. You can direct reads to any of the replicas. For example if replica #1 is unavailable due to a network outage, you can read replica #2 instead.
This thread is about the behavior of FaunaDB, which allows reads to replicas that have older stale values (i.e. they're not up-to-date with latest data). This causes the various consistency anomalies that I've been describing. The reason FaunaDB works like this is to make reads faster and to better distribute read load. Allowing secondary/follower/slave reads like this is a common tactic for increasing read performance.
Does that answer your question?