Once again confirming this. Flying mounts will have both flying and ground based movement available, and as such should be useable in their non flying state in ARR areas. Likewise, certain existing mounts, (Ahriman, Bomb Palanquin, and a few others, as well as chocobos), are scheduled to be granted flying animations at a later date, though from the last I heard, with the exception of your company chocobo, they won't be available to use at launch, as the creators have to first create the animations for these mounts. For your GC chocobo, you will have to undertake a side quest within Heavensward in order to allow it to fly......