When a wing intersects a fuselage or nacelle, the lift distribution does not suddenly go to zero. The lift distribution extends across the fuselage or nacelle with a dimished magnitude. How much the lift decreases depends on the width of the fuselage and the turbulence it generates. Also, fuselages can generate a little lift of their own if they are operating at a high enough angle of attack.

The reasoning behind some contest rules (FAI) requiring the tail to be included in the area loading calculations is to allow for tandem wing and canard configurations. In a normal, wing first, configuration where the tail is a small fraction of the wing area and the plane is trimmed for stability in pitch, the horizontal tail actually produces a downward force in level flight rather than contributing to lift. Accurate performance calculations require that the lift distribution of the entire aircraft be taken into account. Any departure from an elliptical lift distribution increases the induced drag. A wing that is interrupted by a fuselage, boom, nacelle, etc. will likely have a reduced effective aspect ratio.