You're right that I've never seen it in patch notes or other gospel. I remember coming up with the experiment using a FAC with a speed comparable to that of an NPC missile, and I thought I remembered it working, but I guess I can't swear to it. Note that it should also apply to forward motion, so... if I was right, I'd think folks would've noticed something was up with moving vs stationary to-hit effectiveness being off. Seriously starting to doubt myself on that point, now.
That said, should be an easy experiment to do (or re-do?); I'll check it out this weekend and report back.