The base function of this reality is to read, process, and write data in a highly immutable manner. This is conservation of energy. Collaborators in this reality exchange data in a variety of ways, but visual inputs through the mind's eye seem to be the predominate method for memory recollection. Based on causal interviews with individuals since learning I have Aphantasia, it would appear these "internal" views seem less immutable than "out here". Some can zoom their mind's eye. Some see in black and white. Some see icons.
One hypothesis to explain the "shared" part of the hallucination would be the existence an immutable shared data structure underlying the universe which uses consensus to agree, long term, about what happened "out here" based on various and sundry inputs from an entity's internal view & resulting action(causality). Internal views may be non-immutable (highly mutable) and may be influenced by metaphysical phenomenon. People see things that others don't see. The Romans thought it was the act of Gods to see and hear things others didn't.
We've always assumed our brains are making these images up, but perhaps they aren't and we missed something important along the way.