What's even more interesting is if you win, they despawn, where submitting and jumping has them chase you.
That depends on the type of NPC. Sometimes the ones that are sent as a result of cargo or passenger missions will keep coming even if you win the minigame. Quite often they respawn ahead of you, which is even more annoying.
It is too easy though. I can't remember the last time I lost one either. I've had a couple of what should have been close calls, when I've completely misjudged the swing and gone in the wrong direction and ended up with half of the red filled in, but even in a slow trader I've always managed to pull those back to victory. And that's with a relatively sluggish HOTAS.
I'm not sure how easy it would be to balance the game for every combination of player and controller, but certainly a mistake like that should be very difficult if not impossible to recover from.
Actually it's not the AI that's the issue here; it's the variability of commander capabilities.
And controllers. I believe mouse and keyboard offers an advantage in the minigame although I've not personally tried it. I experimented with a console controller and found it difficult, but I guess those who are more used to the twitchy analogue controls would fare better. It certainly handled a lot differently than the HOTAS.
I've seen a lot of anecdotal evidence suggesting that many, possibly the majority of, PVP players use mouse and keyboard both for fine fixed weapon alignment and the interdiction game. Not directly related to NPC difficulty of course, but it's another variable in how difficult FD have to make them to cover all combinations of player ability and controller.
Short of tweaking the NPC response according to the currently active controller, it's hard to know how they could balance this one.
But making a mistake in the minigame should definitely be more difficult to recover from. And losing one needs to be painful. Not necessarily ship loss painful, but I'd expect a trade or passenger ship to have serious hull damage, lost cargo and/or angry passengers following a failed interdiction avoidance. I always run unarmed bulk ships shielded, but rarely above the minimum required for the hull mass, and even back when I used to lose interdictions it was rare for an NPC to get in enough shots to drop the shields before I jumped out.
They're not a threat, just an annoyance.