Wasn't it stated that the information machine Thoth left messages for Porshion? I always assumed these were the Hand and Mask elements in the Inner Voices segments.
Not that simple actually.
Inner Voices chapter 12:（Recorded by Thoth, leader of the Western Scholar Society）
Webnovel 1: The Great Information Accumulation Engine 《Thoth》
We have absolutely no reason to believe that these are one and the same entity, although there likely is some connection. My personal guess is that the former gathered all of the info (possibly including actual chara dialogs and not just the arm/hand ones) and then stored it in that Engine.