I've done aikido for 3 years and have never come across a sensei telling me that "moving the pelvis" is fundamental in aikido, nor has Ueshiba, Shioda, Tohei, etc. have talked about it. You are talking hot air here.
None of those men have talked about the importance of koshi
? I'd find that very hard to believe.
Edit: And I know that Buck wrote "pelvis" and not "koshi", but the term "koshi" includes the pelvis.