Cannabis use reduces dreaming but it does not usually completely prevent it. It's important to remember that THC is only a partial agonist of the cannabinoid receptors. It doesn't completely block them in the way heroin can block off endorphin receptors or methamphetamine can block off dopamine receptors. So it's unlikely that you can pin any dramatic effects from THC like complete cessation of all dreams when it is only partially affecting its receptors. A partial reduction is far more likely than a total prevention of dreaming because of the partial agonist nature.

You need to keep in mind that there is enormous bias against cannabis due to the hysteria of the War on Drugs that continues until this very day. Claims about its dangers and downsides are heavily exaggerated and need to be taken in the context of the political hysteria that surrounds the substance.