It appears that the language in Delta's international contract of carriage was last modified in 2022, but it still leaves open the possibility that Delta will provide a voucher for the inter-airport transfer. How this plays out in practice these days for LGA <==> JFK transfers, I do not know. From Rule 5:

"Although Delta may assist you in making arrangements for such ground transfer service, you agree that Delta is not liable for any act or omission of any such independent operator. If we issue you a voucher to cover the cost of services provided by any such independent contractor and you decide not to use the services, the voucher for such services will have not [sic] refund value."