How can we ensure that all vendors enter tracking information through Marketcube and not Shopify?

For a vendor tracking information can be added in via Marketcube and/or their Shopify store. This information is then relayed to the operator's store and is same which ever method you choose. It would be helpful to understand why this would be required as currently an order cannot be completed without a fulfilment step however it can be added in Marketcube or via vendors live connected Shopify store.