I spent nearly twenty years flying four engined jet aircraft and there was strong emphasis on using symmetrical reverse thrust during an engine out RTO or an engine out landing, allegedly due to directional control problems.
Now for the last seven years or so I have been flying the B767 twinjet and it is SOP to use the remaining reverser to the full during an engine out RTO or engine out landing and I've had no directional control problems whatsoever.
Several decades ago I was involved in a medevac in a Herc and had a prop failure which required an outboard engine to be feathered and even though the requirement for symmetrical reverse was fully briefed for the approach full reverse on the remaining three engines was inadvertently used with no real problems. It was an extremely long duty day which started late at night and arrived back at base just after dawn. We both looked at each other in stunned surprise after the landing roll ended and commented on the requirement for symmetrical reverse.
I can only conclude that the four engine procedure was developed when there were no large twin jet engined airliners and has become part of the culture though possibly unnecessary.
Regards,
BH.