No. A gear train is just a transfer of force/torque. It's analogous to a simple lever for rotational motion. Mechanical impedance is almost always referring to harmonic forces (think of spring systems and structural dynamics). Impedance in fluids also fall under mechanical impedance but it's usually classified separately as acoustic impedance.
I think what they're getting at, and is valid, is how the speed/torque relationship is similar to voltage/amperage. There's nuance which can separate those ideas.
