Isn’t déjà vu just your brain storing something in memory quicker than another part of your brain “looking it up”? In other words it’s a race condition on a dictionary insert.
That doesn't explain predictive experiences - I've been here before, and I remember there being a drinking fountain over there [point's to far left at said drinking fountain]. Of course I can't rule out the possibility that it was seen on arrival but not consciously noted, but it was totally out of frame based on the way we got there and my friend whom I said that to was baffled as well.