iOS 5 Maps used JPEGs for every map tile to render. In comparison, iOS 6 Maps uses vector data (essentially small text files) to create the tiles on the device. Only requesting satellite imagery (for “Satellite” and “Hybrid” modes) requires the same heavy file downloads as the older app. By design, iOS 6 Maps data usage has a many magnitudes smaller impact on network traffic than its predecessor.
Thus, relying on network traffic analysis to measure usage is 100% unreliable as, quite clearly, the different mechanics of the app distort the proportions dramatically. Ignore this report.