Why is this 'cset of P4JOURNAL' carried out only on master or edge server? Why not commit and other types of replicas? Does 'master' also imply that this setting is made for standalone servers (ie. those without any form of replica attached)?

It was changed so that it only runs on a master server. A commit server is a master server. We do not want this to run on edge or replica servers since that can mess up the check sum values. Also, the cset will get replicated over to the replica servers so we don’t need to run the cset on a replica.

Thanks for clarifying, Rusty. There is often a distinction made between master and commit - not always required, but figured I'd check if this was an explicit "not commit" decision.
I set P4JOURNAL explicitly for each serverid in the system - p4d -"cset replica#P4JOURNAL=...." - rather than the generic approach. Helps to give serverid-specific names for the journals in situations where there's more than one Server on the same machine.