Reality is subjective; that is the entire basis of the Madness. It would not work if the realities were shared, but then, if reality was shared, would there be any such thing as madness?
Madness string 1032
Post-Awareness Stage 4 is where serenity and the ability to recall singular memories gives way to confusions and horror. It's the beginning of an eventual process where all memories begin to become more fluid through entanglements, repetition and rupture.