I can say for sure that 'hunger cannibalism' absolutely happened. Hunger cannibalism has been reported to have taken place in basically every part of the world throughout human history during the worst famines, but nothing suggests that the chinese in particular did this more than other peoples when they were starving. Hunger cannibalism has even happened in more recent history, for example during the Siege of Leningrad in WW2 or in North Korea in the early 1990's. Exact sources of cannibalism in the ancient world, in particular the eating of children is hard to come by. However, I find that it is almost a given that this has happened during many famines where cannibalism was the only way to survive. There is no doubt that children have been eaten because of famine in China and in other parts of the world. Even in recent years there have been numerous confiscations of pills or capsules in South Korea containing powder ground from infants and fetuses.

What is more debated is the prevalence of ritualistic cannibalism, endocannibalism and medicinal cannibalism. The latter has been a big topic in China for a long time, but I don't know the prevalence and scope of this.

Chinese cannibalism is well documented to the point that it became a sort of historiographical cliché so some academics doubt if it actually happened as many times as it was recorded. The records can be very terse, for example they will give the year and the location, followed by the words "starvation, the people ate each other. (人相食)" If the historian wanted to give a more vivid image, they might opt for another term 易子而食, which means to switch their children to eat them. So it actually exists in the historical record, but whether it actually happened or is only the imagination of the historian is anyone's guess.