I feel like the definition of plant based also means different things to different people. The most logical definition of plant based is the exclusion of animal-derived foods, full stop. But I've also seen people use plant based to mean plants and also small/moderate amounts of dairy/meat. Hell, I've seen "plant based" used on grocery store product packaging before, even when the product contains dairy or eggs. So I wonder if that's where the confusion comes in from referring to some diets in this study as "plant based" when they clearly have animal products.