ABD has changed their policy regarding arrival transfers, but departure transfers remain the same.
If you book post nights through ABD, and the Grand Californian is your only option, transfers remain intact.
If you book post nights at any other location (including the other Disney hotels), you would be responsible for your own transportation to the airport.
You are welcome to do this and it may make sense financially, but if included transfers are important to you, then your post nights must be booked through ABD.