The remaining piece of the cap screw is threaded into the arm and has no tension on it at the moment. Accordingly, if the threads were reasonably clean prior to assembly, there is a small clearance between the threads of the cap screw and the threads in the arm. Therefore, it will take minimal torque to remove this last portion of screw. It might be possible to rotate it with your fingers or with a pair of needle-nose pliers.

If, however, the screw was forced into some old, unclean threads...........all bets are off with regard to the aforementioned recommendation.

I've broken many 3/8-16 SHCS in the shop when I didn't use the torque wrench..........the remaining piece always backs right out with little effort. The components are new, however.