Client B’s write will only be successfully read from 1 of the nodes it wrote to, and read-repair only runs on QUORUM reads. So, no, it will not be possible to read value 2 for 5m - it will never be visible to operations at QUORUM.

This would have been a valid criticism of LWW (and there are other more contrived examples), but I think (or hope) this is an explicit trade off made by anyone using Cassandra in eventual consistency mode. There are strategies to prevent this being a problem for workloads where it matters, some discussed elsewhere in the thread.