Sounds like there will be no synchronous replication and instead there will be a background process to "constantly keep [read-only clones] up-to-date". This means that a stale read from an older read replica can occur even after a write transaction has successfully committed on the "primary" used for writes.

So, while the consistency is not "thrown away", it's no longer a strong consistency? Anyway, Kyle from Jepsen will figure it out soon, I guess :)