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 toughest critics of all.
Q: Why is it recommended not to refrigerate it?
A: It can be stored in the freezer, but should be brought down to room temperature before opening, and then not kept in the refrigerator after it's been opened. The reason for not keeping it in the refrigerator after it has been opened and while you are using it is because the bottle will get cold, and then when you take the bottle out of the refrigerator into a warmer room where there is humidity, when you open the bottle, warm moist air will enter the bottle and the coldness of the glass will cause the water in that air to condense out into the bottle, getting the powder wet. And then you close the bottle back up. This is why it should be kept in a cool place in the room so it stays at room temperature, so the powder stays dry. But you can store multiple bottles in the freezer to preserve their freshness, just be sure to let the bottle acclimate a day at room temperature before opening.