I suspect it was a skill that at one point someone thought would be good to include but it didn't make the final cut, and sloppy copy editing (I can comment on that since I was a professional copy editor for 5 years) meant that it was removed from the skill list but not from the skill cost matrix. Which means you can either choose to ignore it, or decide how you want to fit it into your own game. I personally only use it for vehicular attacks from the air onto ground targets but it looks like your interpretation is more general and applies for all attacks descending from above.
This does however, remind me of something else which I would find really useful but I can't find either in the SM2 rules (including SpaMCos 1 & 2) or Star Strike - how do construction armour types work against hand weapons (i.e. of the marks 1-5 range that the PCs will have)? At the moment I've been doing OB penalties, critical reduction, concussion hit reduction... or a combination of all three. My brain is telling me that I've read something, somewhere, once, but however often I look for it again, I cannot find.