I think you guys take these PBL units as panacea … actually units itself or light values that you set not so important… you can set anything you want and calibrate your scene to 18% grey (See rosegoldslugs post)… and you know what? it will be correct even if values that you put for lights or exposure are different from web charts for real world values for different lighting conditions… what you are actually do is just trying to bring values in Engine to that values from charts for real world to the same value… which in the end give you the same correct 18% grey value and so on … but the difference is that you can control your lights (Outdoor) but photographer not… so they search their “correct or what they think is right” exposure manually too … because conditions are so different and so many factors affect values. Sometimes even 45 angle differents in shot require different exposure values… And dont forget about shot in photographie is static and you need correct exposure for every angle view what is too not possible to create… so… what you try to do is a little no sense and only help in lookdev to calibrate your assets with consistency…
And here start to play role lighting ratios… sun and shadows for outdoor and fill and key for studio … as example for outdoor 1/4 or 5 for typical direct sun light and here you can set anything you want…5000 sky, 20000 sun or 20000 sky and 80000 sun and calibrate both to 18% grey with exposure will give you same result in the end but with different exposure value…and both will be correct