OK, I'm not a doctor, but presumably that 1-5 seconds difference is very significant. The higher temperature pretty much guarantees permanent damage. The lower temperature at least gives time for clothing to be removed, etc. And the McDonalds coffee was served at least at 180F, so presumably it would definitely cause 3rd degree burns instantly. That just seems way to risky, to me, to be serving as a beverage, which most people would not expect to cause instant 3rd degree burns.