I agree, Valtiel is definitely mentioned in that site absolutely, he is mentioned in the "another crimson tome" and in the "tarot card" area, I forget what it is called sorry.
I mean, I don't even know if the now defunct SH4 site( I mean the original one that translated memories is based from) is even accurate in itself.
However I will say that if the Konami Official Silent Hill 4: The Room guidebook is indeed accurate and truly from Konami/Team Silent, then whatever is in that book should be clarified as a good source for us fans. (I have yet to get my hands on that book).
I don't mean to be a pain in the ass, I just like good sources, for all we know, maybe you are right and I am wrong, it is possible, and like I said, I will happily admit my faults, even if it makes me look like a fool.
So any information that I can find, I will help contribute here, and guide people correctly ( I mean without overstepping people's opinions and beliefs).
I will update in the future if I find anything.
All love here