He's not? I've seen him mention multiple times that HPS will warm the surface of the leaf above ambient room temps, resulting in higher leaf temp, and photosynthetic rate. And that he suggests that LED users, because of lack of IR radiation, would need to increase the ambient temp to subsequently increase leaf temp, to reach similar photosynthetic rates, at the same ppfd.
In my words, the efficiency numbers you guys make the end all, end all, are really just moving the goal posts to make the tech more attractive. Ppfd doesn't directly translate into grams. Pure plant metabolism translates into grams. So why not use a metric that measures electrical efficiency of light vs photosynthetic rate or metabolism?