Yeah, that's another level, and it would be exponentially more expensive, but that's what arms races do. The benefit to these hobby-level drone bombs is that they are cheap.

That said there were already two drones here, one attack drone and one observer, so it's possible they couldn't easily identify which was the attacker. Add three or four just manually piloted and you make it much harder to defend against, even without special swarming tech. In the end you only need one of them to go off, the others could fly back home and be reused.