Actually, the ack tracks and fires only to the closest target. With a single plane diverting the ack any other plane can attack any target without being targetted at all. This is also true for CV strikes, four jabos diving over the CV at the same time (but one after another) will shink it by sure with all the ack concentrated on the first jabo until it is dissintegrated while the others drop their bombs without opposition.
It would be much better for the ack to choice randomly between several targets in range, not just only the closest one.