The description of “Attack Frigates” (for example, goes for fighters/cruisers as well) says: “To avoid engaging these ships, delete this behaviour”.
Which it did…way back before version 1.3x.
Right now removing the behaviour causes the ships not to fly towards the target ship class, but they’re still shooting at anything in range, even though they don’t have attack orders for it.
This greatly messes up the post-combat statistics, as all the missed shots from my cruiser lasers (when aimed at fighters) distorts the big picture (I want to know how well the guns perform against the target groups I assigned them).
Also, it (slightly) preoccupies weapons, most noticable when they have a slow refire rate. When an enemy frigate comes in range, but my ship just fired its missiles/laser/whatever at a fighter, the frigate will have the opportunity to close in fast and be the first to shoot. This is not what I intended
If this behaviour is by design, I would like to suggest a “Do not shoot at X”-behaviour.