does a twin engine lose its gyroscopic properties of inertia?

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He doesn't even understand his own question lol.

Inertia is the tendency to resist change in motion, as described by Newton. He is referring to torque, which doesn't affect yaw, but affects roll due to the third law of motion that every action has an equal and opposite reaction; hence a prop spinning left will make the aircraft roll right.
When a prop affects yaw, this is the corkscrew slipstream effect, of which is corrected by angling the keel on some aircraft.

And a diagram just to help you:





But, counter-rotating and contra-rotating (to some extent) cancel out these effects, at least under my understanding of physics.