The TPS we use for our throttle assembly is actually a potentiometer. It's the same one as used by the OEMs, though, and they overwhelmingly prefer them to Hall effect for the usual reasons (good enough reliability; much lower cost).
It is true that the Hall effect sensor is fail safe in that a loss of either power or ground should result in 0V output. On the other hand, Hall effect sensors work by producing a voltage proportional to an external magnetic field, and guess what there is plenty of in an EV? External magnetic fields. They are so strong at 1000A that the 2/0 motor cables on our dyno push apart a good 12-18". It never fails to amaze people the first time they see that. No one expects big cables like that to move on their own
At any rate, Hall effect sensors can be shielded from external magnetic fields, but it just makes the whole assembly more expensive and, well, the pot in a proper automotive-grade TPS (not the kind used in some golf cart controller's "pot box") will generally have an electrical life of 10 million+ rotations.