I’ve got XT cranks on mine, it has that little plastic plate ( #9 in the diagram) & I’m not sure what it was originally for.
With everything tightened up & over 3000kms of dirt spun out underneath it, I did not use a torque wrench – just my hands - & still no concern over whether it was over or under tightened.
Although with cranks, as long as you’re using a regular allen key without some extender for greater leverage, then you should be applying the kind of torque required to fix these bolts without going overboard & adding to the amount of parts your originally started with... .
Just alternate tightening each one as they get tighter, to balance the tension between the two bolts.
So from me – No not necessary.
Just a bike & a place to ride.