For redundant tasks, yes, agree.

For sharded tasks.  We could be sharding because of the computational limitations of one thread, in which case multiple shards could exist on the same machine.

This is actually a limitation on the current RealtimeManager too.  The incantation to merge runners together properly should be

toolChest.mergeResults(factory.mergeRunners(exec, adapters))

The exec can just be an Executors.sameThreadExecutor().