What does airflow in the sump pit mean?
I am a residential builder, but I would suspect this "air flow" is best explained through psychrometrics and the concept of "natural draft".  

The air inside the drain tile system will likely be much cooler than the temperature in the basement.  That temperature difference begets a pressure difference, with the cooler air being more dense than warm air. Nature, forever seeking homeostasis, tries to reconcile the pressure difference between the two areas..... and a draft is formed. 

This phenomenon can also be known as the "stack effect" when dealing with building construction, and is one of the causes of thermally inefficient homes.  Improperly sized HVAC systems and things such as ventilation fans in bathrooms and range hoods will also serve to depressurize the house.

From a building inspector's point of view there is absolutely nothing to be worried about.