When a coupling (rigid) is designed to drive through it's face friction, should it be necessary to add the additional cost of "fited bolts" as a security matter?
I hope that you are talking about a clutch and not just 2 flanges facing each other without bolts.
The bolts are what carries the load.
Spend the money to get the bolts.
No, it is not necessary to add fitted bolts to a rigid coupling when all of the torque can be taken by the friction in the joint. The fitted bolts just add to the cost of both the bolts, and the manufacture of the rigid coupling. make sure that the friction in the joint is adequate, and that the bolts are tightened correcttly.