People agree on where the front of a car is, but I've found that people disagree on what "in front of that car" means when the car's headlights face away from them. (A similar but perhaps slightly different sort of ambiguity is that I've found that people disagree as to where the bottom of a cup is that's held upside-down.) Non-geeks in each case, FWIW.
People would usually agree that the side of a mobile phone with the display is the front, and that the side of a camera with the display is the back, so I can well imagine that there'd be confusion as to which side is the front when a mobile phone is being used as a camera.
If "some (geeks, I expect) find it confusing", then that's already reason enough to try to find a better way of describing a tablet's camera direction than "front/rear-facing". [As for ‘"normal", non-geeky people’, doesn't that exclude LWN readers almost by definition?]
Other than "inward/outward-facing" or "user/(scene?)-facing", some possibilities might be "self-facing" or "display-side".