Now that you spoke about it...lol. Knowing Nomura that might actually be a twist he throws at us.
The past of worlds is also sent to sleep and found in the RoS...0_o
That would not be a mindblow but a mindbonk le grande...considering what then could all be witnessed and explored in this realm.
if this were the case it would be a bit easier to explain why theres a mickey from the past there, and it may help in explaining why theres a mickey in the RoL (King Mickey) and supposedly 2 in the RoS. (TCoM and Fantasia)