The system that has the property set in my environment is 5.5 so I will confirm that this is true for 5.1 as well. Another idea is to confirm if the HBA queue depth was set on the ESXi hosts (or if they were left to default). I used the following link to determine which HBA was installed on my ESXi servers and settings.
VMware KB: Changing the queue depth for QLogic, Emulex and Brocade HBAs