That's right. I think Billy is doing that.I dont think we can read into the MB experiment what isnt there.
Yes the added GHGs were larger in percentage but smaller in total projected cross-section. So the experiment is unrealistic both ways in quantifying atmospheric physics. However I think that it does demonstrate qualitative aspects. Those who don't believe in back-radiation at all will have a hard time explaining the results unless they resort to unsubstantiated bold claims (like SSDD)the controls were standard air, they added massive amounts of CO2 and methane far beyond what is naturally present.
I have repeatedly called for a realistic experiment using actual natural numbers. The temp increase would be small but present. Unfortunately all we have are experiments like this that compare at 200:1. And most of the others are outright fraud, like Gore/Bye.