When a website has shown the item is back order only.it is because of Backorder Rules. The rule is added below
For example, you create a sales order with two items – item A and item B. Item A has sufficient inventory, but item B has no inventory. If you create a configuration with just one rule and no backorder rules, a location is assigned to item A, but will be blank for item B. You will need to select a location manually for item B. If you include a backorder rule in the configuration, the automatic location assignment engine can assign a location to item B. Item B will then be marked as backordered.
we can change the back order only item to out of stock on the website.The solution is added below
When an inventory item has the field “OUT OF STOCK BEHAVIOUR,” the field is currently set to default. So the backorder behaviour is showing . When we can change the field to Disallow back orders but display out of stock messages then the item availability is zero and the item will show as out of stock. The screenshot is added below
