I now have a Pertronix ignition and it has a start retard built in. I have not tried it. If what they say is true of the rotor stopping in the wrong spot, then this box probably would not be any different, but again I have not tried it. I always thought it was because mine was added on after the fact instead of built in.

Reasons to lock the distributor:
-Better Idle
-Easier to set total timing
-One less thing to go wrong
-Some cars really like it locked better than a curve.