DreamerV3 number of rollout_workers

Medium: It contributes to significant difficulty to complete my task, but I can work around it.

[RLlib] DreamerV3

I run tuned examples of DreamerV3 of Ray RLlib 2.9.0 repo. These examples run smoothly.
However, One question arise:
why num_rollout_workers=0 is set in all examples?
If set num_rollout_workes> 0, an error shows up: DreamerV3RuunEnv has no for_eachpolicy()?

My question, why DreamerV3 can not scale up by using num_rollout_workers>0?