It also functions as a way for imperial nations to clean their own history. Initiation into a gang/secret organization might involve an act that prevents you from backing out of the organization in the future. For example, corrupt officials before allowing a new member into their circle will likely involve that new person in corrupt acts as well, its to build dirt of them similar to what they have themselves. This way the new person will be hesitant on acting against this group as they will be going on a suicide mission.The Xinjiang genocide talks are strictly for domestic consumption. The allegations are unprovable by default and so outrageous that no one in China believes them. Xinjiang is not a black box like North Korea. Millions of tourists visit it every year and if China have done even 1/10th of the things they accused China of doing, legitimate evidence would have leaked out.
In the context of Xinjiang, the Western imperial powers will built a narrative of "Chinese colonialism" for both domestic and international consumption. This narrative initially creates strong sentiments, over time sentiments fade, some become jaded. When no tangible action is taken against China, people subconsciously assume the normal nature of colonial acts irrespective of whether the narrative against China was real or not to justify their past as a way to build cultural/historical confidence. We will hear more revisionist narratives. The international narrative component aspires to be a tool to prevent China or any other challenger to use anti-colonial ideology against traditional imperial powers.