The news article hits on two big snags in the negotiations between the Allies and the USSR. First, the Soviets were concerned about having to do all the heavy lifting since, they claimed, Germany was virtually “unassailable” behind the West Wall. Second, the Allies were concerned about the fighting effectiveness of the Red Army in the aftermath of the officer purges. Each side had valid concerns.
While the West Wall was stronger on paper than it was in real life, the Allies had no stomach for attacking Germany from Alsace-Lorraine, as they so clearly showed in September. Thus, the USSR had a genuine concern that they would wind up doing all the fighting.
As for Allied concerns about the effectiveness of the Red Army, the Red Army was actually far worse off than even the Allies realized. I’ve read “Stumbling Colossus: The Red Army on the Eve of WW2” by David Glantz, the preeminent American authority on the Red Army in WW2. He portrays in stark terms just how woefully unprepared the Red Army was from 1939 to 1941. And he makes clear that based on their own internal documents, at the highest levels of command the Soviets knew they had serious problems.
When you add the Polish intransigence about allowing Soviet troops on Polish soil (and for good reason) it should have been apparent to the critical observer that the concept of an Allied/Soviet Pact was a non-starter in 1939. The Non-Aggression Pact should not have been a shock. I guess we’ll read about that in the next few weeks.