The reduced frequency is because instead of two trains running on a continuous loop, from the main terminal to the north satellite to the C concourse, they now have just one train shuttling back and forth between the main terminal and the north satellite.

The south satellite (NW, US, HA, BA, SK, etc.) went through this back in the May/June timeframe, and it was a terrible pain in the neck, especially for evening arrivals -- it could take 30 minutes to get back landside from your arrival gate.