A while back, I told my husband "No, you can't train swift flight form. You must do the quest at 70. Your alliance druid exists so I can have the Raven Lord on Birdfall and I'm not going to let a little training incident waste all that time!"
This last Sunday, my husband helped his best friend finish the druid swift flight form quest, the quest you must perform to summon the boss (Anzu) who drops the mount.
This is pertinent because he'd already trained swift flight form at a trainer.
Therefore, this has been confirmed by someone I know and trust. You can do the swift flight form quest for the summoning capability even if you train.
Also note that the moonstone goes on your keyring and just stays. It no longer gets used up.