This can not be. SENSE = the LOAD voltage. Even the FET internal body diode should make it about 7.2V
Either FET is defective, or it is bad wired, or SENSE connection is bad wired.
****
When battery is present (with Auxillary)
...
Auxillary Voltage: 9.42V
... SENSE: 9.42V
That schematic is correct.
If you read the description right above Figure 3, it describes how they are using the chip as a comparator and not in the linear mode as with the other configurations.
My simulation of that configuration also works.
Had almost given up on this circuit and had left it the way it was on my desk for last two days.
Today morning when I turned it ON (with no changes made at all), It seems to be working fine... I am completely puzzled why this was the case.
Till now its working fine. Let me see how it goes.
Meanwhile when auxillary is connected, will there be any voltage at the drain. According to the body diode details there shouldnt be but I see some voltage there, even when battery is removed.