My experience of arriving at Terminal 1 at JFK on JL and had connection on AA flight out of Terminal 8. It seemed like connection counter at Terminal 1 could only accept baggage if baggage was already tagged to the connecting flight. Connection counter at Terminal 1 was not staffed by an airline representative but by a contract employee who was handling all connections. Looked like could not look up your connection reservation, could not print out luggage tag, hence looked like connecting baggage was accepted only if your baggage was already tagged to your connecting flights.