Well, your firing is still limited to arc, after your ship has moved. This simply gives you greater odds to make sure your big gun(s) can find a target.
Really, I don't think it matters much except for boresights. At long range, non-boresighted ships usually don't have problems finding a good target for their main weapon, and their backup weapons may not be in range of anything anyway, so a "Concentrate all fire!" order is more useful. At closer range, an arc'd weapon is more likely to be able to find a target than a boresight, but now you want to be able to fire more secondary weapons, so CAFing usually isn't what you want. Typically you're looking for more maneuverablitiy, or defensive orders when it becomes a scrum. So it becomes a real drawback to have to use a special order to get the boresight off. It becomes a serious choice.
Chern