Used fuel weighs more than the raw fuel, it’s just outside your vehicle in the typical use case. As you have shown, a typical assumption made with fuel burning vehicles is that disposing of the effluent is free and you can just throw it overboard.
Anyway, my point is just that when comparing two aircraft, and their fuel sources, it’s probably worth just comparing the closed system of the aircraft and measuring the environmental impact of fuel sources separately.
Obviously we won't do that, but it's worth considering what the apples to apples comparison would really look like.