If you kill the enemy ships before they fully pull into formation, they will spawn indefinitely allowing you to rack up infinite amount of points as long as you keep their initial formation from forming.
One way to solve this is to disable the Enemy’s collision box during the arrival animation.
I noticed the same thing, but posted (here) before seeing this topic.
That sounds like an interesting idea. Coupled with the ships getting larger as they show up, it seems like it would kind of make sense as well - you can’t hit them until they’re “there”.