[5555624]

That could be more of a problem. Regardless of the height, dumping a battery means a projectile falling, which could injure someone or cause property damage.

If fuel is dumped high enough, it pretty much evaporates and doesn't fall to the ground. If the plane is low when it dumps fuel, it can hit the ground and bystanders; but, it's not going do much, if any damage. (Assuming it doesn't hit someones barbecue or a smoker.)

[GravitasFailure]

Don't forget that lithium batteries tend to burst into flames if you hit them hard enough. Dumping your batteries can too easily become a bombing run.

Also, Jet-A doesn't burst into flames like gasoline. Even if you soak an area with it, you don't have a firestorm just waiting to blow up.