Seems so. And they don't seem to know about it, they might even see each other as "the person who stole my desired position"
And it might actually be true in a sense. It seems the girl who wanted to be Zuikaku was so skilled that the superiors decided she was better as Kaga. And the girl who wanted to be Kaga was rejected, not achieving the expectations, but since a slot for a Zuikaku was opened, they called her to fill in...