The rabbit hole in question being why the hell anyone in the government in the '80's actually believed that these things could "defeat police body armor," which is why there was a big scare regarding them and they're now federally regulated.

Spring loaded ballistic knives are a novelty at best. I'd be far more concerned with a theoretical ne'er-do-well stabbing me normally than pinging a ballistic knife at me with which he only gets one shot anyway.