Hello,
When using the permanent reverse mode (with shift) together with the motorized platter, the effect of sound deceleration and acceleration occurs a quarter of a second after the sound has started playing backward (or playing forward, when switching back to forward reading).
The track is actually reversed at normal speed for a quarter of a second, before slowing/accelerating according to the platter torque.
Beside audition this can also be observed by looking at the playhead moving on the waveform.
It looks like the software triggers the reverse reading before taking into account the platter rotation.
v. 1.6.1.