Most of the late model knock-sensed cars we have had on our dyno run right on the knock threshold stock - we have a gadget that lets the operator listen to the knock sensor in headphones during a run - there is a lot of activity from the sensor and micro adjustments going on all the time. Tapping a bolt on the head lightly with a hammer sees the advance drop and return almost instantly.
The only conclusion we can make is that the knock sensor in our Jacks is not so it can run on the raggedy edge of detonation (the ign adv behavior proves that) it is so it can 'see' crap fuel.
Rodeo is considered a tradesmans ute and would spend its life in metropolitan areas and Jackaroos are intended to go into BFN - the Rodeo lives where good fuel is the norm and the Jack could be somewhere where there is only crappy fuel. Your VX's may be programmed similarly to our Rodeos, using the knock sensor in the more 'normal' way
Recovery of a broken-down 4WD costing upwards of $10K are not unheard of here - it is possible to get a looooooooooooooong way from anything at all