Why indeed would the now dead be any more able to predict the future than when they were alive?
I can imagine answers to that.
The first is that people who have NDEs and other transcendental experiences, and purported messages through mediums, always report the same thing..that that other "place" is timeless, that past, present and future all exist at once there etc.
That to me invites more questions than it answers. Namely why do the dead get in touch or reassure us at all - if the physical world is effectively an illusion, everything is going to be alright and no real harm ever comes to us no matter how it seems, and if that post mortem realm is timeless, why do they give a toss?..in effect we're already up there, so there should be nothing to reassure us about or any need to waste their time invading our dreams or appearing at the foot of our beds!
So an alternative is to say not that they see every aspect of our futures but rather that they're watching our lives from a different perspective and therefore see more of what's coming up.
Any kind of survival of death presumably means vacating both the physical world where time is measured by the movement of heavenly bodies like the Earth and sun, and also the physical brain where our ordinary and flawed conscious perception of time is shaped. Outside of these two limitations, how could they not see more of the future? Given your psychic saw yours in such detail suggests that future is there to be seen, if one is viewing it from the right perspective.
So imagine your life as a car being driven along a long winding road. You see it unfold from the drivers seat, and are fully in charge of making decisions about how fast to go, where to turn, when to stop. But the disembodied's perspective is that of the Eye In The Sky -a helicopter pilot reporting on the traffic - looking down on the whole scene. He's not seeing into the future per se, but does see everything on the road ahead that you can't. The traffic jam or obstacle you're heading towards, the oncoming truck around the corner etc. He can make a pretty damn good guess what's going to happen, so can try and alert you to slow down, stop or change direction.
In other words from your viewpoint that traffic jam 10 minutes further along your journey is an event in the "future", but from the viewpoint of someone looking down its something that's happening "now" that you're just not aware of yet.
I don't know any of this to be true, I'm just saying if hte dead do survive and there is an afterlife realm, then being able to tell us what's coming up seems an almost inevitable consequence of that new perspective.