Webley A&WC (screw grip) and PHV1 (treble bite) actions are renouned for their strength and part of that is due to their third bite systems. Excellent design, quality materials, and skilled workmanship are also responsible for the Webley reputation.

A well designed and well fitted third bite should add to the strength of the action.
This is only true if the gun is in original tight condition.
Guns that have been shot considerably in a loose condition, and are later tightened on the hinge pin or hook, are a different story altogether.