In a ki67, I have landed damages in upwards of 6-7k with 1 sortie.
Unless someone comes up with a detailed explanation how the displayed damage at landing is computed, I would be quite reluctant to use it in an argument like this.
If you put 3k on a Vh and destroy it, you still get less "landing damage" displayed than dropping the same amount of bombs on a town center, even though all of the destructive power of you bombs had been used to kill that hangar. Several smaller objects within blast radius give you more points. So you always have to keep in mind the targets someone was bombing.
Also displayed damage at landing and the actual damage points for score are not directly related to each other. Once i bombed 6 town centers with 3x1000lbs each, and then 12 town centers with 3x500lbs each. Using the 1k bombs, i usually land between 32-35k damage, with 0.5k bombs I landed 50k - but the damage points I got for score was about the same.