Broken communication - Lack of responses

I want prove of this.
I cannot find any documentation backing this up. (besides on rumor)
Not to mention that there is barely any content epic ever released which follows this.
Not to mention:


So unless something changes after cooking, or someone comes with prove I am going to assume this Null/NAN thing is not true.
Additionally, if this is true than it would mean specular would never work unless the metal value input is set to zero instead of “no value”

No really, I want this to be clarified for once and for all.