As per the FCTM this NNC is written for the FFM inadvertently activating and now 3 PCU's are powering the rudder, thus avoid large and abrupt rudder pedal movement
First there are only 2 PCU's on a 737. A main and a standby PCU. The FCTM refers to "3 control values" (where 2 are controlling system A and B pressure inside the main PCU).
Second my FCTM say that:
"FULL rudder inputs should be avoided", in this condition. Not "Large and abrupt rudder pedal movement", which should be avoided at all times (see American Airlines A300 crash).
My question:
1. What will happen if large or abrupt rudder pedal movement is applied. Will the rudder break?
To reformulate your question: What will happen if FULL rudder pedal movement is applied?
I think you mix up aerodynamic forces with internal loads on components inside the rudder.
As mentioned, the system A and B hydraulic pressure powers 2 pistons in one PCU. The standby system powers a separate PCU. The rudder won't break, but perhaps (my best guess) the main and standby PCU may not operate perfectly synchronous, and at full deflection, put unnecessary load at the components.