I am sure there were...interesting...incidents to make the military want this.
yes there were/are reasons for it.. The major reason is the possible situation of hydrostatic lock in multifuels .. Crank that engine while providing fuel and if even just one cylinder has liquid trapped while the engine has firing power providing torque and momentum during cranking, you will get
Incident #1 : BANG ! Soldier has successfully busted a piston, or most-likely, soldier has successfully completed task of bending a rod(s) on the errant cylinder(s) which can lead to more-serious damage before engine gets shut down .. The idea is/was , if soldier cranks engine without providing fuel, the starter by itself is not strong enough to break engine nor bend a rod if any cylinder has a liquid obstruction.. The piston will supposedly stop, starter stalls and goes GRRRRRR, perhaps melt a battery post to make the event just a little exciting.. Personally never had it happen but it had happened a time or two in my last BN.. We all know Murphy. The one time we fail to check for something is the time it can F-up..
As far as electrical reasons, I know what you mean.. Have had construction equip that prefers the switch turned off before pulling the kill lever, and vice-versa.. However, in the army of my experiences, we never discussed if there was any electrical reason.
It was always about hydrostatic lock in multifuels, and also,
Incident #2 , Soldier fails to leave kill knob pulled out at all times after shutdown with truck in neutral w/brake set, chocks if not on level terrain.. Explanation: multifuels will start and drive off by themselves if the engine stop is in and they are parked in certain gears, regardless whether the acc switch is off or not.. Of course they need gravity or an accidental push or whatnot to get them rolling, but it did happen here and there