Barley grass is not the same as wheat grass. Indeed a whole book is devoted to the differences between the two. A notable difference I'd like to mention is: if you consume an amount of wheat grass juice that will make you throw up, the same amount of barley grass juice will not. So obviously, they are not the same. If you want more specifics, they're here.
I have used the recommendation of this product in my practice with great success, and there are hard science reasons for this, and the empirical evidence can't be argued with (well, it can be, usually by people who don't want to believe that we need to take a nutritional supplement).
NOTE: I'm providing these links below as a service; I do not make any money from you purchasing this product. And I believe in doing business with good companies that deserve our dollars, and the company that sells this product is one of these companies.
By the way, kids love it too, and kids are the harshest critics of all.