Doesn't change the fact that Demon hunters are Demon hunters and not daemon hunters, since blizzard are the ones that make the lore.
Knowing the daemon spelling isn't really tied to age either, considering that spelling is used by Games-workshop for it's warhammer franchise, it's about as fanciful as knowing there are dwarfs and dwarves.
Really wish that they would let us use the wings in caster form, and then when we morph into meta, we completely morph, as if the wings are side effect of being so... demonically infused, i guess would be the correct term. With this, as we build up our demonic fury, we look more like we are about to burst out all demony.