I'd considered the dog eating grass thing as more of a now-disputed myth, but maybe someone has evidence. Either way my own dog loves munching on the taller/thicker grass every time we walk, like he's a sheep. His favourite foods also include broccoli and bok choy so that could be why. I think a lot of people downplay the role plants play in a dog's diet (not required but helpful especially with processed diets that can lack organ meat etc), and they don't always get fed them at home.