A fault, that is the source of the vibration, could be in either the driveline (u-joint, center bearing, centering bushings, etc.), or in an axle shaft (bent shaft, bad CV-joint, loose splines). The other element, be it the axle shaft or the driveline, then may be vibrating in sympathy, at the ratio of the final drive - 3.07:1. The element which is at fault is the driver of the vibration, and the other element is being driven. The use of the word "contrariwise" was to indicate that each of the elements can be either driver or driven.
[Just as a curiosity, a 3.07 final drive has tooth counts of 15 & 46.]

The frequencies that have been observed are way below the first order (natural) resonant frequency of any of the driveline components, let alone the frequencies of 2nd or 3rd order harmonics.