Someone timed my engine once with the Nu-Rex wrench and I have a stock distributor and points. It ran terrible, when I got the car home I reset it using a volt meter as described in Les Andrew’s book and it ran perfectly. I bought one of those wrenches and the Nu-Rex timing indicator you can bolt onto the front of the engine and when I used the wrench and checked things with a timing light there was over 40 degrees of advance and the timing was never retarded.
I take the wrench along in my on board tool kit so it can be used in an emergency to get you going again on the side of the road but for me that is not the way to time your engine as a habit.