According to the documentation, If the On Receipt Release option is selected, the system generates an inventory receipt and a transaction that updates the expense account when the purchase receipt is released. The system updates expense accounts for both stock and non-stock items in this case, and the system does not update any inventory accounts.
Even though my settings are as stated above, no expense is booking with the PO Receipt release. It only books once the AP Bill has been released.
Before AP Bill:
After AP Bill: