No, it would just have to reach the target interception area in time. That's not quite the same as "catching up", although of course the possible radius within

No, it would just have to reach the target interception area in time. That's not quite the same as "catching up", although of course the possible radius within which this area must be located shrinks as a function of speed ratios. And if by "flies over it", you meant the defense system as "it", that's still effectively point defense. Although this particular situation is unlikely for obvious reasons; the chance that your defense system would be exactly below the flight path of a missile while not being its target is small.