In my experience, the problem with the dial back lights and multi-spark ignitions is...... They "seem" to be working fine, even when they aren't.

I've seen this happen on the dyno a few times where the owner of the motor being tested has brought his timing light with him.

Sometimes the dial back lights agree with the no dial back lights...... Sometimes they don't.

I've seen this play out several times.

No dial back lights and msd for me.