This is, as the kids say, cap.

Popcorn works because the outer hull is strong enough to hold together until a critical mass of pressure builds inside to rupture it. At that point the starches, which have liquefied under pressure, explode and unliquify rather suddenly.

White rice and pearled barley have their hulls removed. You can see in the picture that the barley has split, but not popped, and the rice just looks a little blistered. These will never pop like popcorn.

It is possible to pop some other grains like popcorn, but none of the ones listed here, at least not using the methodology described. Puffed rice and wheat are done in machines that lower the air pressure to create the same conditions as popcorn.