[pclmulqdq]

The implicit assumption that you are making is that all cropland is fungible and that the 43% used for animal food can be converted directly to human food. That is almost certainly not the case. Also, the original comment's 86% doesn't imply that it is necessarily "cropland" - just that it is land that grows animal feed.

You see this with human crops too - Why do people grow corn when almonds are much higher dollar value per acre? Why not wine grapes? The reason is because not every patch of land is suitable for high-value cash crops. Going down the quality scale, not every patch of land is suitable for food for human consumption either. The reason why is that "cropland" is not fungible - soil has particular characteristics, nutrients, contaminants, and microorganisms, all of which affect which crops you can grow.