They can spawn in from nowhere, twist around like snakes, and interdict you before you even spot their canned comm chatter.
If you drop supercruise to try and lose them, they manage to follow your wake unerringly within seconds.
If you supercruise away from them again, they spawn in front of you, drop behind, snake-spin again, and you're interdicted again.
They don't seem to suffer 'the spin of doom' from interdicting you.
They can spam chaff for days, or at least as long as whatever internal cooldown they have tells them it's okay to.
Farming a hazres or combat zone or comp.nav all day? That's fine, until the game decides a fleet will spawn in on top of you.
There are loads of ways that NPCs, in fact, 'cheat'. And it makes the game less fun.. because the ordinary tactics you'd use to deal with other ships just don't apply. You can't wait out an opponent's supply of SCBs. You can't outmaneuver an opponent in supercruise because the game has rolled the dice and decided you're going to be interdicted this run, no matter what, and no tactic will prevent it. I can't be the only one who finds this frustrating and wishes I had more realistic opponents that I could actually counter and use strategy other than 'Destroy!' against.