What they literally mean is "the model of nutrition we are using does not predict the association". This is evidence that whatever model they're using isn't com

What they literally mean is "the model of nutrition we are using does not predict the association". This is evidence that whatever model they're using isn't complete. Nutrition science is still under rapid development, and its epistemic rigor is not yet very high. There are many reasons that plant-based diets are theorized to cause health issues that are not yet conclusively proven or disproven, such as the effects of plant fat profiles on human metabolism. Plants are certainly not chemically fungible with animals, and popular nutritional models do not incorporate many details of this.