Web, “while the sane point out that without a GHG effect and uniform spectral emission/absorption in place, the average surface temperature would be 255K and then due to the lapse rate, the temperature profile would get cooler with increasing altitude.”
Prove it. The only way that it would be 255K is if the exact albedo was present for the No GHG Earth as for the real Earth. With a nitrogen only atmosphere, there would still be an atmosphere with temperature predominately controlled by conductive heat transfer. With a nitrogen and oxygen atmosphere, there would still be a warmer atmosphere, predominately controlled by conductive heat transfer plus there would be a stratosphere. Green house gases change the rate of heat transfer and the distribution of heat and a large percentage of that is also due to the conductive properties of the greenhouse gases.
Do the nitrogen only atmosphere thought experiment. You tend to over simplify which ironically over complicates things.