SubGrids that are embedded in a QuickView forms do not display data when creating a new where the form contains the QuickView form.  Instead the embedded sub grid displays "To enable this content, create the record", even when the data could be available.

Example scenario, on the case form add a Contact QuickView form to display data regarding the Responsible Contact.  Once the responsible contact is selected the QuickView form displays field data for the selected contact, however any SubGrid on the QuickView form will not until the Case is saved.