ORIGINAL: blw
Unloading in the air is another way of saying that the propeller disk has become more efficient. It is that simple. If you are seeing 10,000 RPM on the ground when WOT, you may see something like 11,000 in the air at WOT. It's not due to more fuel being drawn into the carb, it's due to the propeller working better because of the inflow of clean air.
Regardless of why the prop unloads the engine is spinning faster with a WOT. That means it is using more air, and it needs more fuel to keep up. So it is using more fuel. If it did not need more fuel it would not lean out.