The literacy claim is absurd. If you understand what is required to learn to read and write Chinese, you realize that a huge percentage of the population doesn’t have the natural memory required to be anything more than semiliterate (no population does, for that matter). Moreover, away from the cities, the rural poverty is quite extreme, and the amount of time people have for memorizing characters is not great even if there is a teacher.
My sons read and write Chinese - we know the effort and the ability involved to achieve a reasonable degree of literacy.
Are you Chinese? Would you recommend I have my young children learn Mandarin? Opinions vary on this.