Lore for me does not only mean "things exist"...but also availability and "commonness" of things. According to conan "lore" there is almost no limit to imagination (especially if you count in the comics and later books), but do these things really exist as mounts for the common hero?
There you as devs are responsible, since you can manipulate that "commonness" by ingame availability, price, power etc.. Even though lore might say a flying dragon is a really rare mount for some kushite riders in the far south, if you make it available by the shop and make it one of the most powerful and useful mounts in the game, you are responsible for changing a "really rare" mount into a "really common" one. Another example is the tiger...lorewise a unique locally bound and specially trained mount for a chosen few...does it feel like that when you visit the OT trader?