No. Vermiculite came later in recipe. Cakes can and will fruit without it. Vermiculite is suppose to keep the cake from drying too quick. It's a casing.
I've found rolling the cakes in vermiculite makes a bigger mess and it sticks to the stems of the shrooms. My last crop wasn't rolled in verm and had 4 flushes per cake. I've grown more cakes without it then with it.