Advanced movement allows for flocking behavior. This type of movement behavior is commonly seen by flocks of birds or schools of fish. There is more movement behavior, such as queuing, which tells only one unit to go through a door at a time, for example. Squad behavior is great when you have units that protect each other.

The advantage of using movement behavior is that it doesn't require additional decision making for your AI. This also allows you to take some of the computation out of the tree and calculate it on the pawn.