The Batch Shipment Screen shows up if:
The "Ship From Location" field is left blank in the Sales Order. (See screen shot - BlankShipLoc)
Since you may have multiple locations where you can Ship from, the batch shipment screen will pop up to show you all of the locations and the qtys. at those locations that you can ship qtys. from.
You will then be able to select the Ship From Location and Process the Ship Doc. (See screen shot - batchshipping )
If you have on the Preference to Always try to add the items to unshipped Ship Dos for the same Customer & Location you can create on Ship Doc for Multiple Sales Orders. (See screen shot - mulitplesos)
You can set that preference by going to Company>Preferences>Company Preferences>Shipping>Filling Sub-tab> In the section for When generating Ship Docs from Sales Orders using the Batch Shipment screen: Always try to add the items to unshipped Ship Docs for the same Customer & Location. (See screen shot - batchpreferences )
The the line items have multiple ship dates or ship to addresses on the order. (See screen shot - multipleshipdatesadd.)