I have yet to understand the decision of having a needlessly over complicated real world lighting measuring methods in a realtime game engine where the notion of anything related to how real light works in the world is absent in the first place, from true reflections to realtime or even accurate baked GI to bounce lights to true area lights, to shadows and self shadows you name it.
Even in offline renderers these methods of measurement are rarely used and most of it is eyeballing with approximate exposure values.
Why take this route? Just keep it simple exposure stops and temperature values (similar to Arnold) only a handful of occasions in the CG world will someone resort to measurements in Candelas and lumens Not even majority of VFX in Hollywood movies or animated films at Pixar use this!
Everyone is trying now to match realworld settings in a game engine and expecting super accurate results like a camera, well good luck.
From time and time again as much as i like this engine I am constantly disappointed at the priorities and some of the decisions taken when there are so many basic things that require immediate attention that would actually make a difference.