I wouldn't say Stalin was cynical. In fact, that would be more applicable to Churchill and Roosevelt. When Italy surrendered, Soviets argued for a joint occupation. Italy was one of the countries that attacked the Soviet Union and was in war with both allies and the Soviets. They were flatly refused, more than once. So, after bitching about it, they decided to act according to the precedent set by the Allies - whoever occupies a territory decides what happens to it.

Lets not forget that there was a strong communist movement in Italy at the time and given the 100% free elections, it is not unthinkable that communists would have been placed in power.

So basically, what Stalin did in Poland was not different to what Allies did in Italy, and according to Glantz, Red Army was indeed at the end of their logistical supply and was unable to mount a huge operation of capturing a huge city such as Warsaw at such short notice...