The first response I received from Delta via email incorrectly quoted Delta's domestic Rule 30 and said I would be responsible for transportation. The follow up response indicated they would take care of it.
Thank you for contacting us.
You may go to the baggage service office at JFK and they will help you with ground transportation to LGA.
Delta Provided Ground Transfer Service Between NYC Airports
See International Rule 30 for Delta's guidelines regarding complimentary ground transfer service between JFK -and- LGA / EWR.
Eligible passengers must go to the baggage service office for assistance with transpiration arrangements.