I... think there is a good reason for this.

The vibe I've got around the Gridanian quests is that the forest was harmed far more than is visible on the surface. Explicitly, the elementals themselves were harmed and are thus less prominent, as if they are hibernating to survive. (Or are maybe being surpressed by ascians.)
This would explain why no random elementals are running around anymore and we are only seeing the volatile sprites.

As for their graphical representation not matching the name... that is certainly awkward. They can't use the iconic elemental model without calling them elementals. Maybe there would be a more appropriate name? I'm not sure what, though...

...I can live with Sprite.