i might be mistaken there - but NPC ships follow different LoD ranges or visibility rules. - you can see a player destroyer at 14k ( when you look hard and know where it ought to be ) - but you cannot see a NPC so far away - i think they disappear faster.
but its an interesting observation none the less. - wonder if anyone else has similar issues - that way we could determine if its the mod or the settings.
If the NPC ships don't disappear, I don't think it's the Ship Detail in the Options; when I had this issue for that reason in 4.84, NPC BHG caps were also invisible...