Yeah that was getting too lengthy for the meme bottom text though, so I just went with "tanks". But yeah, it is wildly inconsistent. Sometimes you can shoot down a ship and get 15 kills. Other times you get 0.
I think it depends on if you hit the ship before the tank/bot has started dropping. If you can hit it while it's still completely on the ship, I think it works. At the very least, I've seen tank corpses stuck in mid-air after the ship goes down.
I've had it happen, but it's very inconsistent. I'm not sure if you have to be host for it to work, but I've had a very small handful of tanks die to the falling drop ship. It seems like the ship has to land directly on the tank's gun pod to work, which is hard to do because they spiral down.
It's slightly more consistent if you get lucky with drop ships that clip into each other, as sometimes both of them will go down and both do explosive damage on the ground.