Sure you don’t have to be as close to the target, but any terror group that could obtain top of the line military hardware and smuggle it close enough could probably smuggle modern hardware that’d do the same. The video makes it seem like the equivalent of a terrorist group armed with top end missles today.
And usually groups that carry out terror attacks don’t care about being found out, the whole idea of “we don’t know who did it” wouldn’t really matter to them.
It’s scary to think about these things until you realize, if people want to cause terror, they can. Today anyone who could setup an attack with explosives could tape them to a drone and strike a person. To me the real question is how can we stabilize international relations and reduce the number of people who are thinking about doing things like this.
If you want something to be scared about, be scared about what the result of global warming will cause when climate change leads to turmoil and further global strife. That’s an outcome that will be deadly with or without “slaughterbots”, that we can actually start trying to solve, instead of preemptively hindering our own technological advancements