On the 782 (much like the 682's) the early ones physically stayed in the on position after PTO was selected.
Later ones physically returned to the neutral position after PTO was selected as they had a relay that was actuated by the PTO switch, so the switch could return to neutral position,but PTO remained on.
This was in compliance to newer safety rules in the reverse interlock circuit.
So as stated, serial number break is important.
It prolly was when MTD took over but I have not researched it.
IIRR it was so the PTO stopped when reversing the tractor.
That way you could not run over yourself sitting on the seat, while backing up
