The vicious lie about Serbs perpetrating genocide in Croatia, Bosnia and Kosovo was repeated so many times, that when one see "Serb mass grave found" (or "Serbian mass grave found") in the headlines it is understood as mass grave of people murdered by the Serbs, quite opposite of what it stood for.
That means that the repetition of the lie was intentional, to cover up real crimes.
The same technique is used to depict Auschwitz and other German Nazi death camps located in occupied WWII Poland as "Polish death camps".
To lesser extent, Turkish genocide of Armenians becomes "Armenian genocide", not "Genocide of Armenians".
For most it’s easier to apply spin than to admit truth, in the case of the US and their muslim proxies, it’s simply easier to outright lie.