I think I understand your concern. Basically, SRM and the SRA handle the LUN replication and VM protection and recovery. As long as your LUN replication is successful and your SRM configuration is correct, you do not have to do anything in the DR site with regards to the replicated LUNs. The "Placeholder LUN" is the pointer to re-creating the VM disks accordingly on the replicated LUNs and DR Hosts will "own" them in DR scenario.
You should be able to "test" your recovery plan which should highlight any issues and this should be a regular practice, maybe monthly, as any changes in Live may affect your DR plan.
I hope this makes sense. If not, please ask.
Regards