The reason for the Frillish scene was that the writers needed some female Pokemon for James to get excited over so that Mareanie could get jealous about it and mess the capture up. That's all. Then they probably just took a look at some Mons with gender differences and thought Frillish was fitting (since it's kinda similar to Mareanie).That Frillish fixation is outright weird. Even if it didn't mean the writers wanted to forget BW, it still was just odd. And considering TR relinquishes all of their newly caught Pokemon except Wobbuffet, this is even weirder.