I test every hooklink, every leader knot, if I can snap it, then sure as heck a fish can.
I'm relying on a gradual increase of pull, strength, but a carp uses its speed. Within a metre it can be at top speed, that can be enough to put the tackle to far more tension and pressure than me.
Fluorocarbon as far as I know has different abrasion resistance and although the stretch is similar, it's elasticity is less than mono. Mono can stretch and go back to its original state, whereas fluorocarbon, can't it tends to 'ping' quicker than mono.