I've read many survival books and you can also stay alive by eating poo. Surviving and a eating food of optimal nutrition are two different things. During the Irish Potato Famine many resorted to eating grass and they also starved to death with a bloated stomach full of undigested grass.
I define wild foods as edible to mean our bodies can gain nutritional benefit from it, not that we can eat it and nothing bad happens. Otherwise it would be poisonous. Certain types of grass is beneficial (like wheat or barley grass) but needs to be juiced or ground up to break down the tough cellulose. I was disagreeing by the generalization of grass as all being edible and beneficial. Edible wild greens like dandelions and clover and specific types of young grasses, like you said, have less rigid cellulose and so can be digested with our single stomach and give us nutrients. If I went outside and started eating a significant amount of saint augustine or crabgrass in my yard I will most likely vomit like my dog or at least have intestinal distress to rid me of it.
I've found that dandelion greens (I juice them because they taste really bitter) have noticeable effects on my energy level. I have not noticed this with wheat or barley grass or really any other green, though I've never grown and harvested my own fresh barley or wheat grass and this could make a difference. Dandelions are packed with the most nutrients and minerals than any other green or grass. They are downright medicinal.