Are you talking about on either side of the hinge looking at the phone from the hinge side?

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I had not noticed before, but yes there is a gap at the hinge side. I believe that is because the distance is fixed on that side by the hinge. The other side closes tight with the hinge action pressing the edges together. The gap provides clearance so the tow halves of the phone don;t rub as the hinge opens and closes.

I have been documenting my experiences with the backflip if you want to check out my ramblings.