The 'unphysical', 'inexplicable', 'spirituality' that is nevertheless elicited by 'physical' substances and/or practices is contradictory. We must seek explanations like we do in science. In the case of the information we get via psychedelics, eg DMT, we must settle down the question as to whether they are comming from other worlds or the always exist hidden in the brain.
DMT is said to mimick serotonin. One of the functions of serotonin is to 'tell' the brain cells to 'sleep' (hence to dream). So when DMT bind to serotonin receptors of some cells, they begine to sleep. However, the brain still can detect less serotonin. Therefore the brain interprate the presence of DMT as a very different kind of sleep and hence a very different kind of dreams.
We relate sleep to unseen worlds the same way we relate night to stars. Though the 'unseen' is always there, the wake state eclipses the information.