When you edit an item model, if you include the thirdperson_righthand tag and don't include the thirdperson_lefthand tag, the scale, translation, and rotation values of the right will also apply to the left.

If you specify the thirdperson_lefthand tag and not the right, it will only apply to the left hand, not both hands.

My expected result is that the thirdperson_righthand tag would only apply to the right hand.