Dear Phillip,
The SWRT model has no gearbox (GBRatio = 1), so, I would expect the low-speed and high-speed shaft torques to equal (HSShftTq = RotTorq), but I would expect some difference between these and applied generator torque (“GenTq”). The difference may be small for your case, though, because the generator inertia (GenIner) is small for the SWRT. More information about the drivetrain model in FAST is available in the following forum topic: Resistant moment of the rotor and of the electric generator (in this forum post, RotTorq is identified as LSShftTq; both are equivalent).
I suspect what you want is the applied aerodynamic torque (what the forum post linked above calls “T_Aero”) instead of the torque transmitted through the shaft (“RotTorq”). While applied aerodynamic torque is not currently a standard output of FAST, some guidance on deriving it from the available FAST outputs is given in the following forum topic: Aerodynamic Torque.
Best regards,