My understanding of that - Because of the Torque reaction from the motor and spinning prop, it (was) common for a single engine craft to turn better/faster in one direction - (opposite prop rotation) - over the other. With the P38's contra rotating design, that wasn't an issue and therefore the aircraft could turn equally fast either way.
Not quite, Scott.
Contra rotating was not the dangerous part, it was which WAY they chose to turn them.
Under low angles of attack, the propeller produces an equal amount of thrust on the left and right side, regardless of rotation.
When the aircraft is at high angles of attack, the side of the propeller that is descending produces far more thrust than the side that is ascending.
The P-38 arrangement has that thrust on the outsides of both engines, far from the aircraft centerline. When you are pulling hard and turning, this blows more air over the ailerons, enhancing roll responsiveness.
That's all good when both engines are making power.
If one quits for whatever reason, now all your thrust is way out there on one side.
This plus lack of experience killed many an early P-38 pilot. It would enter a spin rather quickly.
If they had rotated the other direction, the thrust would be very close to centerline and much safer.