It had not much reserves, and they were sent to where famine was. Also, some of food shipment that was supposed to be sold to West was reverted. There are lot of documents confirming it, including critics from the West for failing of food shipment obligation.
Collectivization can be considered a reason of 1933-th famine, but not because it was a change to the worse, but because process of change from individual to collective mechanized agriculture was pretty rough. Imagine what would happen in Civ if starvation was not switched off each period of anarchy.
But after collectivization was completed, regular famines that was hitting Russia each several years before, was ended.
If you want an example of a forced famine, I'd recommend to look at Ireland, 18451849.