Dear Ohiana,
Your question is similar the question discussed in the forum post found here regarding why the rotor torque does not equal the sum of in-plane moments: FAST: Why does RotTorq exceed the sum of in-plane moments?.
For the rotor thrust, the thrust is based not only on the sum of the out-of-plane shear forces at the blade root, but also on
(1) the sum of the axial root forces projected on the shaft axis (due to precone),
(2) the weight of the hub projected along the shaft axis (do to shaft tilt or tower deflection), and
(2) the inertia effects of the hub do to e.g. tower deflection and yaw rotation.
Of course, the expression is fairly complicated in the presence of shaft tilt, tower deflection, precone, etc.
I hope that helps.
Best regards,