The rail is a ultra high density, high stiffness component. A minimum of EPS 200. It identifies the beam below and lets the ground worker walk with confidence.
Long term only the density and therefore stiffness in this peak stress zone resists load. If your floor design suggests material less than EPS 200, it can not carry the load a Gdeck floor can. If you have built a floor with light weight material in this zone, perhaps the beam and the screed are closer than you think.