Going back to the M135, all of the SAE terms:
On-Demand Synchro Variable Torque Passive System
On-Demand Synchro Variable Torque Active System
On-Demand Independently Powered Variable Torque Active System
seem awfully fancy compared to a system that was of the same vintage as the early LandRover described above (only slightly fancier in being linked to the reverse shift position, the truck had an automatic transmission as well to simplify driving). The variable torque of the M135 is basically binary, either engaged or not.
It would seem that the SAE J1952 standard was first published 1991,(well after the M135 and LandRover were designed)
https://www.sae.org/standards/content/j1952_199101/ and to be a bit picky is only intended to apply to light trucks up to class 3 which seems to top out at 14000 pounds GVW.
https://en.wikipedia.org/wiki/Truck_classification It isn't clear if this is the same class 3 definition SAE is using.
I could facetiously claim the 4wd system on my F350 is also "on demand" - when I demand power to the front wheels by moving the floor mounted shift lever, power is delivered.
I wasn't trying to tell anyone they were wrong, only to suggest that are a large variety of systems that can't all be neatly pigeon holed.