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Given what's already been confirmed here I'd be reasoned to assume that the credits for this OP are somewhat in order (Sugiura before Mitani before Mori), which makes this scene all that stranger.

According to GreenJumper's spreadsheet with all the KAs for the show (kudos to that btw, real nice) there was apparently a NC animator on this OP, so I'm guessing that this could be their part. I just wonder who it could be.