Calling pm_handler_secure_on_connection for every BLE event

In pm_handler_secure_on_connection, I see that it only looks for BLE_GAP_EVT_CONNECTED events if PM_HANDLER_SEC_DELAY_MS is not in use. I also see the comment "In normal circumstances, this function should be called for every BLE event." What is the reason for the latter? What are the circumstances where I can just call it when a BLE_GAP_EVT_CONNECTED event is received? 

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