It is nonsense. USSR was supplying Germany with critical war materials right up to the attack (which Stalin had been repeatedly warned about.)
Leadership in the Red Army had been decimated during the Great Purge three or four years prior. Executions and imprisonment included all officers above Major or Colonel.
The Red Army could not have invaded anyone, probably not even Finland. One of the major reasons for the initial German successes was this lack of leadership,it had to be re-created on the hoof.
It explains a few things to me. Armies on defense do not generally mass at their borders, if the Soviets were getting ready to attack it is easy to see why the Germans took all those prisoners right at the start. If the attack By Germany were a hurried response to an anticipated attack by Russia it would explain why there was almost zero preparation by the Germans to fight in the winter, unless you believe the German General Staff were idiots and failed to anticipate there would be a Russian winter. Those are a couple of things I have wondered about over the years that make sense when looked at as the book describes. I won’t dismiss it out of hand.