SomeCarGuy,
So watch the video. You will see that the timing light has no dial back. It is a "fixed zero" timing light. NO DIAL.

Rotor, reluctor,pick up and cap all stay in CONSTANT PHASE at all rpm. The only exception is while using vacuum advance.
The only change is the shaft delay to the engine.
If you think that a timing light wont tell you when spark is occuring, then you cant be made to fully understand what a distributor does.