When you eject, the "player object" is the falling seat, not the pilot. So the camera is slewed to the seat and you can't controll it. When the seat is destroyed (when impacting the ground), the camera goes to the pilot, but only 3rd-person view.
Edit: it looks like it works when ejecting from the WSO seat
Edit 2: you can still controll the plane when being the ejected WSO