I honestly don't know so these guys' explanations are as good as any. I'd just like to know why this bothers you unless you're just picky like me. I wouldn't think there's anything you're going to be flinging broadheads at out at 70 yards and I personally couldn't see any reason to practice with broadheads that far. I know it makes sense to practice that far just to perfect shooting form, but field/target points would suffice for this.
If You're Not Living on the Edge You're Taking Up Too Much Space
Martin/Rytera Staff Shooter
PSAA Life member, UBP Life member
PADI AOW Diver