Broken communication - Lack of responses

[Deathrey (DeathreyCG)]

@MikeViolette;744895

Hi everybody,
Metallic and PBR
We do require that all materials be PBR and have Base Color, Roughness, and Metallic inputs. While it may look as though Metallic defaults to “0”, it actually defaults to “NULL”. There may be no noticeable visual difference, but the engine handles the material differently. With no metal input, it is not entirely a physically based material because lighting would not take into account whether the material is a conductor or insulator (dielectric or metal).
UE Marketplace Content Coordinator

Pretty sure that metallic scalar material input gets compiled with default value of 0 if it is unconnected, and has absolutely no effect whatsoever, thus the doubts about forcing authors to plug in zero constants for nothing.