There it was. A thread buried in the support forums titled: "How to deploy V-Ray in offline environments."
V-Ray 6 Material Library: Offline Download and Installation Guide
(this step requires temporary internet access or pre-downloaded files in that path). Transferring Existing Libraries vray 6 material library download offline install
A valid account is needed to download the files from the Chaos Downloads page. Step 1: Downloading the Offline Material Library (v6)
Best Practices for Studio Asset Management There it was
, moving away from the standalone folder-based local library used in older versions. Offline Installation Steps
Download the multi-gigabyte library once and distribute it to multiple local machines. Step 1: Downloading the Offline Material Library (v6)
Setting up local material libraries on multiple render nodes without needing separate internet connections for each. Prerequisites
There is no need to rename or unpack this file! * Place the downloaded MaterialLibrary file next to the universal installer. ... *