Also in my reading of jhana states(8) is that while in a jhana all five of one’s senses have been withdrawn, making awareness of ones one body impossible.No sounds, smells, tactile sensations, sights or thought processes. A sense of duality between a doer and doing or a knower and known also disappear. One is in a state of absorption and only after the jhana has finished does a self reemerge and world.
On emerges back into the sense world and has access to what happened via memory and can use for the next several hours the strength of focus to access past life memories and various psychic powers.
it is very useful if understood as a tool for focusing and reflecting on Buddhist topics (sattipana sutta) and not and end in its self.