The orifice is a flow restrictor that limits the maximum amount of gas that can flow to the burner.  When installed, it is the component that determines that maximum flow of the gas to the burner, and which directly impacts the flame height.  Control of the flame can also be accomplished with your key valve without the artificial upper limit imposed by the orifice.  Consumers usually like this level of control, since they adjust the flame from a roaring fire to a mellow, soothing one.

The CS burner is not a listed burner, so we have no requirement to impose an upper limit on the flame height.  The CS burner is the original sand pan burner in the industry, designed by TR Rasmussen in 1958.  It has never been shipped with an orifice. 

Installation without the orifice does not adversely affect the safety or operability of the unit when installed in a fully functional wood burning fireplace.