why does the over center spring have to be removed

I don,t want to harp on this , just want to give a better description of what my clutch pedal is doing . as said in another post I had a diaphragm unit put . the clutch engages from a dead stop when is just about to the top. pushing down to shift , pedal about half down and it disengages pushes easy. but after half way down , it real hard to push down to the floor, like I said in other post , OC SPRING was not removed. is this causing this weird pedal action or is it some thing to do with the clutch spring that is under the car and hooked to the bell housing?? just trying to give more detail regarding this --thanks for any info