[Sauron the White]

from WCH

The issue is the rather astonishing claim that all the First and Second age material Tolkien ever wrote is somehow 'incorporated by reference' into the Appendices.

Could be please cite the quote where anyone made that "rather astonishing claim"? And I would like the exact quote not some rehash, a retelling , a paraphrasing, a translation, an "its the same thing as...", or "it sounded like to me that ...".