I think they introduced the arcane river monster park levels around the same time they introduced the maps for arcane river themselves. But maybe you can answer a question in return. The question is do the arcane river monster park maps require arcane force as well?
You they do, personally i think that is kinda weird, a MonsterParc map that requires (i think it was 100) arcane force. But then again, every lvl210 and higher level player probably does his dailies in Arcance River, I know i for sure do.