This has been discussed before, though no official answer came out.
I've asked people around the boards about this very isse:
Why, do the planes in AH, always, lose both Hstabs, and never just one?
Upto this day, I've never, ever, had just one Hstab destroyed in the MA.
I've seen this happen, in offlline, while target practicing against the drones. A P-51D was flying around with only one Hstab intact.
But, when online, ever since I started AH with AH1 v1.05. I've never ever damaged or been damaged only one Hstab.
Weird, eh?