pinking blades are (generally) used on the raw edges of yardage before pre-washing- such as a large backing- to help keep the tangling/fraying down to a minimum- you would not be able to get accurate cuts for piecing blocks with a rotory pinking blade.
one way to make it easier to (deal) with the loose/frayed threads on the back of a quilt top is to clean up the back of each block as you make it- instead of waiting until the whole top is together.