Shopify natively offers an option for their shipping that provides customers with an estimated delivery date when selecting options for shipping. This estimated delivery date can be offset with an additional day or days for processing time. This feature is valuable for the customer as they can get an idea when to expect their order and do see if expedited shipping options get them their order faster (i.e. Friday over Monday) whereas "x business days" can be hard to calculate or understand for the average customer.
This feature is lost when integrating with ShipStation and receiving calculated rates. ShipStation sends over "x business days" to Shopify. It would be a great addition for the estimated delivery feature to be included with this integration package!