For spiritual experience to happen, there must be a way in which the seen world communicate with the unseen world. This is of scientific interest. The problem with the famous 'hallucination' idea is that no one can explain how such can come about. When the info pertaining to the unseen comes to the brain, then that whatever mechanism is much close to the notion of 'third eye'.
It is likely that in the usual 'wake' state, the brain categorises info from the unseen world alongside visualizations via the help of chemical signallings from pineal. It does so by dimming these info. So pineal isn't necesarily a direct gate linking the seen and the unseen body. The real 'third eye' is in the unseen body. The hallucinogens (or psychedelecs) mimicks the role of pineal. Some chemicals from pineal tells the cortex how to interprate the infor it receives. So we know the difference between 'real' and 'imagination'. However, in the 'closed third eye', not all the dimmed info is imaginations. Some are info from the unseen!