The terms are still not interchangeable, even if the existence of dragon riders may have influenced the design of dragon knights (Lar posted an early story concept with the character being a phoenix, so it wasn't a direct evolution if there is a connection).
In any case, my comment about dragon riders was less about the name than the fact that the 'dragons' were not free flying creatures, but merely moved just above the ground (unsurprisingly for a 2D game released in 2002).
If the player character is able to fly freely, a third person view with an adjustable camera would be much more suitable than a fixed direction isometric camera. Overhead cameras have been used with some flying games (arcade shooters, RTS games, etc) with size, shadows or perspective to indicate height, but I don't think that would be generally acceptable for a modern RPG.
