Yeah, but how aren't temperature and density related to altitude? For all practical purposes, the two are one and the same. The higher you go, the colder and less dense the atmosphere. Even the thermosphere isn't really an exception. You might find molecules and atoms exited to temperatures that would melt concrete, but the molecules are so far apart (kilometers) that you'd flash freeze if you stepped out into it. Even if you came into contact with any of the superheated gasses, the total amount of energy would be so slight, that you couldn't physically detect it without advanced instruments.
He missspoke. It is related to temperature but independent of density.