Thanks moony for chiming in. I wish you’d make your version of modern (extended) uber surface shader (& even sell, otherwise i would love to donate - haven’t found the time to study it all and organize in a practical group). As you suspected, energy is lost with the shader shown here.
Floki, sure GGX is known to loose E, why multiple scatter came to play to prevent this. Especially in cases where’s lots of glass (most prominent in archviz, why you see mostly artistic approaches (VRay) or ground truth sims with Lux, Maxwell…). But not many apps/tools take that into account (to expensive for games or films even).
Here’s an overlay, where’s much easier to observe the difference:
