The real issue is, why is such a trivial event being reported at all by propaganda press in the West? Civilians are killed almost every day by deliberate Ukrainian shelling targeting them in Donetsk and other Russian-held areas. This is regularly reported in Russian and international (non-western) media. I surmise that reports like this are meant to distort western populations' perceptions, into believing their own press is fairly reporting attacks on Russia when in fact it is not.
Granted those drones are cheap, but it still defies logic that Ukrainians would waste one by lobbing it at random into a St. Petersburg residential area, handing Moscow a propaganda victory.